diff --git a/tests/PhpSpreadsheetTests/A1LocaleGeneratorTest.php b/tests/PhpSpreadsheetTests/A1LocaleGeneratorTest.php
index 64da06639..243705c36 100644
--- a/tests/PhpSpreadsheetTests/A1LocaleGeneratorTest.php
+++ b/tests/PhpSpreadsheetTests/A1LocaleGeneratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/ArrayFormulaTest.php b/tests/PhpSpreadsheetTests/Calculation/ArrayFormulaTest.php
index 65244c5e6..f1847fb64 100644
--- a/tests/PhpSpreadsheetTests/Calculation/ArrayFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/ArrayFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php b/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php
index 60c336cf1..77b5251a7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/BinaryComparisonTest.php b/tests/PhpSpreadsheetTests/Calculation/BinaryComparisonTest.php
index 752c72e15..d1303aefc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/BinaryComparisonTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/BinaryComparisonTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\BinaryComparison;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationErrorTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationErrorTest.php
index 3ebc9888c..9bbaca1a5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationFunctionListTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationFunctionListTest.php
index d13d8c900..d23786cb6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationFunctionListTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationFunctionListTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationLoggingTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationLoggingTest.php
index ac218522a..b9243deb3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationLoggingTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationLoggingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationSettingsTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationSettingsTest.php
index 6363685bd..b205a1d18 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationSettingsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationSettingsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
index 2aba97483..5848d84a1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/CyclicTest.php b/tests/PhpSpreadsheetTests/Calculation/CyclicTest.php
index c754520bd..2357c0bc9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CyclicTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CyclicTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/DefinedNameConfusedForCellTest.php b/tests/PhpSpreadsheetTests/Calculation/DefinedNameConfusedForCellTest.php
index 6f97f9c87..703996d9a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/DefinedNameConfusedForCellTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/DefinedNameConfusedForCellTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Calculation/DefinedNameWithQuotePrefixedCellTest.php b/tests/PhpSpreadsheetTests/Calculation/DefinedNameWithQuotePrefixedCellTest.php
index 0c2511640..695850734 100644
--- a/tests/PhpSpreadsheetTests/Calculation/DefinedNameWithQuotePrefixedCellTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/DefinedNameWithQuotePrefixedCellTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php b/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
index 4f450f57c..d011f3c7f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
index 2aef7837b..9196bcc32 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engine\FormattedNumber;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberTest.php
index 669882948..fef4d66b5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engine\FormattedNumber;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
index 834865d96..9dd9b377d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceSlashTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceSlashTest.php
index 8b652999b..bd94002f9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceSlashTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceSlashTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engine\Operands\StructuredReference;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceTest.php
index d78e7af63..459795701 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/StructuredReferenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engine\Operands\StructuredReference;
diff --git a/tests/PhpSpreadsheetTests/Calculation/FormulaAsStringTest.php b/tests/PhpSpreadsheetTests/Calculation/FormulaAsStringTest.php
index 91b1c5234..aeb13e0b5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/FormulaAsStringTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/FormulaAsStringTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/FormulaParserTest.php b/tests/PhpSpreadsheetTests/Calculation/FormulaParserTest.php
index a913333d9..10ce2cd48 100644
--- a/tests/PhpSpreadsheetTests/Calculation/FormulaParserTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/FormulaParserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
index 5d49069b9..18978afa0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DAverage;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
index f1b0483d9..6ddcfd6cb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DCountA;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
index 01ab75b39..ded350b93 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DCount;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
index 3b50a4ba3..052261604 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DGet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
index 63fffd9fa..2689fa3cf 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DMax;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
index 3095aae82..c1e553dc1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DMin;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
index 45fcd2316..57590ee25 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DProduct;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
index 681f92527..bb80b211b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DStDevP;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
index 21b56a234..73eb7a410 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DStDev;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
index 1312c23f3..3589e8959 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DSum;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
index 592ae985a..c880bb62e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DVarP;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
index cd415abb6..7a0e923f9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Database\DVar;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
index ff0b65293..c280b6725 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Database;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateDifTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateDifTest.php
index fd0073419..f3c1e8916 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateDifTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateDifTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
index 393c3232b..4a1c8762f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
index 987cc3d0d..997987c1e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTimeImmutable;
@@ -41,7 +43,7 @@ class DateValueTest extends TestCase
         Functions::setReturnDateType($this->returnDateType);
     }
 
-    private function expectationIsTemplate(string $expectedResult): bool
+    private function expectationIsTemplate(mixed $expectedResult): bool
     {
         return is_string($expectedResult) && substr($expectedResult, 0, 2) === 'Y-';
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DayTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DayTest.php
index 657984335..83587a45e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/Days360Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/Days360Test.php
index 4b5569db5..b9d9be885 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/Days360Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/Days360Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DaysTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DaysTest.php
index 3cf3ba725..f8cf49468 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DaysTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DaysTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
index 6788ad196..c6f793f71 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
index 762c94aca..996397dae 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/HourTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/HourTest.php
index c26d685cb..68781ffd0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/HourTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/HourTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/IsoWeekNumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/IsoWeekNumTest.php
index 0d9aece43..a2452e0ad 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/IsoWeekNumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/IsoWeekNumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MinuteTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MinuteTest.php
index c6035a690..3c987452b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MinuteTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MinuteTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MonthTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MonthTest.php
index 8ab199f7a..fdb91fff2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MonthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MonthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MovedFunctionsTest.php
index 0d640a483..9aba4adef 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NetworkDaysTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NetworkDaysTest.php
index 09427eaad..0e853040a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NetworkDaysTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NetworkDaysTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NowTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NowTest.php
index c58ed2556..c69239157 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NowTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/NowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/SecondTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/SecondTest.php
index e8a048493..f440ecaef 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/SecondTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/SecondTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
index 2a8f127f9..7d20a0994 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
index c7856f9a4..f10f4aa3e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TodayTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TodayTest.php
index 10152e72a..006ac6bb9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TodayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TodayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekDayTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekDayTest.php
index ee37f6450..e5c42b6a9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekDayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekDayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekNumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekNumTest.php
index 0a0dd4cad..daa0eeb77 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekNumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WeekNumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WorkDayTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WorkDayTest.php
index f18a0fdaf..db9d95d17 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WorkDayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WorkDayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearFracTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearFracTest.php
index 216849058..74157492a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearFracTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearFracTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearTest.php
index 90037490d..e913a5619 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/YearTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DeprecatedExcelErrorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DeprecatedExcelErrorTest.php
index cd31177b6..a2356f7fa 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DeprecatedExcelErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DeprecatedExcelErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselITest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselITest.php
index ebf88d6a3..8a659358c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselITest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselITest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselJTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselJTest.php
index 93ee38dbf..ce8930505 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselJTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselJTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselKTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselKTest.php
index e1f8b60de..8a17b5c82 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselKTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselKTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselYTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselYTest.php
index f4188173f..598cd95a7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselYTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BesselYTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2DecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2DecTest.php
index a79907fa8..06c62b4cb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2DecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2DecTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2HexTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2HexTest.php
index ad2d8ac18..0c92a482c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2HexTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2HexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2OctTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2OctTest.php
index 11e05eedb..7f25427ef 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2OctTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Bin2OctTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitAndTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitAndTest.php
index 40d864787..047ec142c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitAndTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitAndTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitLShiftTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitLShiftTest.php
index 8c3d0b25c..3a21e3f1a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitLShiftTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitLShiftTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitOrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitOrTest.php
index df5dcb92f..b697e9116 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitOrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitOrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitRShiftTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitRShiftTest.php
index a300d6e7a..46f866886 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitRShiftTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitRShiftTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitXorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitXorTest.php
index 50db15fd3..b62c9cc9c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitXorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/BitXorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ComplexTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ComplexTest.php
index da93183f9..93e2352f6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ComplexTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ComplexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ConvertUoMTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ConvertUoMTest.php
index a5f269107..fd9b7bca3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ConvertUoMTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ConvertUoMTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2BinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2BinTest.php
index e9cc77dcb..e29c17adc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2BinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2BinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2HexTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2HexTest.php
index b7e905955..c1fa9de75 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2HexTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2HexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2OctTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2OctTest.php
index 8b7bb59cc..b99608546 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2OctTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Dec2OctTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/DeltaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/DeltaTest.php
index 9a9cdfe79..6824a5e42 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/DeltaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/DeltaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfCTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfCTest.php
index 41f7cb923..fa163bce6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfCTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfCTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfPreciseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfPreciseTest.php
index e96240cfe..0f144bcdd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfPreciseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfPreciseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfTest.php
index f20dfe842..b5c7c6384 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ErfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/GeStepTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/GeStepTest.php
index 8bef63ce2..768cc7129 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/GeStepTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/GeStepTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2BinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2BinTest.php
index 31fb3b20a..261d9c589 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2BinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2BinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2DecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2DecTest.php
index 27822dabe..a9b294254 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2DecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2DecTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2OctTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2OctTest.php
index 5e2b5554d..8ae7ab5f3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2OctTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Hex2OctTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImAbsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImAbsTest.php
index b21c9e3e4..ac879162c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImAbsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImAbsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImArgumentTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImArgumentTest.php
index ef1c731e6..ef8c2dde6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImArgumentTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImArgumentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
index 18003d11a..7dd9b7b90 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImConjugateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
index ac77648dc..5910d26b4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCosTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
index 6e7c6004b..e52b3dee7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCoshTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
index b907769e5..d7ac678b5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCotTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
index 19d12ba1c..7b6c1693e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCscTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
index 07237fe9b..0683326c0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImCschTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
index debbc5637..b07d46a46 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImDivTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
index c52b962d6..985d4960e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImExpTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
index 0a98b0642..0acf60f00 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
index abf9e9581..c552c1949 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog10Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
index 623529a5f..707654b1e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImLog2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
index 2291ee775..e60d6288c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImPowerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
index 3d42f13b0..8e8594821 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImProductTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImRealTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImRealTest.php
index af411c186..185073c35 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImRealTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImRealTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
index 191aeefdb..2b3d1f6f3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSecTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
index 28066f95d..d438f90e6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSechTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
index 42e0825e8..b69bb72d5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
index 62fc1fa6b..651bd4828 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSinhTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
index af6d5c8c8..6ff243020 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSqrtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
index bd25d9061..1d5a18823 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSubTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
index 135fd64ae..99a30c5d1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImSumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
index 0f0814c89..6efb1800e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImTanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImaginaryTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImaginaryTest.php
index 948e6996d..3f4e55b54 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImaginaryTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/ImaginaryTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedBitwiseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedBitwiseTest.php
index 2de8ee769..2a0652a28 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedBitwiseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedBitwiseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engineering;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedFunctionsTest.php
index a98ca605e..f68ea1f2a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Engineering;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2BinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2BinTest.php
index 4a07ec67f..18c602746 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2BinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2BinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2DecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2DecTest.php
index 4a03c2148..bc9b9666a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2DecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2DecTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2HexTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2HexTest.php
index 7b2854b0a..af52760d6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2HexTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Engineering/Oct2HexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Engineering;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintMTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintMTest.php
index 84925f778..07f99cc2d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintMTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintMTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class AccrintMTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintTest.php
index 949731e7f..97bd742df 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AccrintTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class AccrintTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AllSetupTeardown.php
index f267df44f..4d46664c1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorDegRcTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorDegRcTest.php
index 276d4a9a2..459b7674a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorDegRcTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorDegRcTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class AmorDegRcTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorLincTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorLincTest.php
index b465cbd2f..95db9bc19 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorLincTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/AmorLincTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class AmorLincTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDayBsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDayBsTest.php
index 8dced87d4..15633fd8e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDayBsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDayBsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupDayBsTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysNcTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysNcTest.php
index a6332e0b5..7696f61f8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysNcTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysNcTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupDaysNcTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysTest.php
index 71cf96211..f7ba0e7be 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupDaysTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupDaysTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNcdTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNcdTest.php
index d46c55ce1..f3f04792f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNcdTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNcdTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupNcdTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNumTest.php
index 0de8e9562..86360ecb3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupNumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupNumTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupPcdTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupPcdTest.php
index 4a2d6d627..8c02ea048 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupPcdTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CoupPcdTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CoupPcdTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumIpmtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumIpmtTest.php
index db99b0658..a27724ab8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumIpmtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumIpmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CumIpmtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumPrincTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumPrincTest.php
index 9c590cd05..b241c2940 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumPrincTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/CumPrincTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class CumPrincTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DbTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DbTest.php
index a28f1bcd1..13856c048 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DbTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DbTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class DbTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DdbTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DdbTest.php
index 8a744851d..5e513ed64 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DdbTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DdbTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class DdbTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DiscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DiscTest.php
index 038b84084..317854edc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DiscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DiscTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class DiscTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarDeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarDeTest.php
index 5f12331c0..c37937740 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarDeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarDeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarFrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarFrTest.php
index e762bb7e7..992b5a64e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarFrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/DollarFrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class DollarFrTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/EffectTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/EffectTest.php
index be367b2a6..4811c64c3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/EffectTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/EffectTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class EffectTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvScheduleTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvScheduleTest.php
index 878e4986c..bb72492f5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvScheduleTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvScheduleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class FvScheduleTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvTest.php
index 9c67cbc41..1dbfee1af 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/FvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class FvTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/HelpersTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/HelpersTest.php
index 7a7b3a0a9..6cceaf423 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/HelpersTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/HelpersTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Financial\Helpers;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IPmtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IPmtTest.php
index ea2413043..75faf7927 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IPmtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IPmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class IPmtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IntRateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IntRateTest.php
index c9473823e..fc111f1cd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IntRateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IntRateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class IntRateTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IrrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IrrTest.php
index d49c21baf..08d09c587 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IrrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IrrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class IrrTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IsPmtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IsPmtTest.php
index c39c15584..ea085fb50 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IsPmtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/IsPmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class IsPmtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MirrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MirrTest.php
index bf60f52d1..d2a65dd06 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MirrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MirrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MovedFunctionsTest.php
index 4429c522c..e23def856 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 //use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NPerTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NPerTest.php
index 96928c083..302ad808f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NPerTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NPerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class NPerTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NominalTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NominalTest.php
index 136d11871..302d5a0c1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NominalTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NominalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class NominalTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NpvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NpvTest.php
index 94cfa569e..c43d819bd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NpvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/NpvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class NpvTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PDurationTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PDurationTest.php
index 1a25096ed..7c31158e1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PDurationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PDurationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PDurationTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PmtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PmtTest.php
index 41f788463..ae3f6ea9f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PmtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PmtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PpmtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PpmtTest.php
index c8c1cb9eb..820d315d8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PpmtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PpmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PpmtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceDiscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceDiscTest.php
index 480c6fc16..2abb6effb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceDiscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceDiscTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PriceDiscTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceMatTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceMatTest.php
index 46ed4ef34..a30c196b8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceMatTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceMatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PriceMatTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceTest.php
index 293bb6a19..56328f882 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PriceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PriceTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PvTest.php
index 599fee907..ffdb1e25b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/PvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class PvTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RateTest.php
index fb4360c9c..f36437395 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class RateTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/ReceivedTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/ReceivedTest.php
index c75d31999..d5ac3000b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/ReceivedTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/ReceivedTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class ReceivedTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RriTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RriTest.php
index 0e162abb5..ccfd7587b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RriTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/RriTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class RriTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SlnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SlnTest.php
index 59966a0a1..abe5a7a9c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SlnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SlnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class SlnTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SydTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SydTest.php
index 61b871855..6b8561771 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SydTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/SydTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class SydTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillEqTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillEqTest.php
index 9e04c6866..d18aa5285 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillEqTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillEqTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class TBillEqTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillPriceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillPriceTest.php
index 4506d430c..c8778fc28 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillPriceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillPriceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class TBillPriceTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillYieldTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillYieldTest.php
index 37529c57b..30d58c327 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillYieldTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/TBillYieldTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class TBillYieldTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/UsDollarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/UsDollarTest.php
index f15adc1ff..91714a169 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/UsDollarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/UsDollarTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class UsDollarTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XNpvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XNpvTest.php
index c2a011696..a94a9210d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XNpvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XNpvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class XNpvTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XirrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XirrTest.php
index 6df19e5b2..d48bd1b61 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XirrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/XirrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class XirrTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldDiscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldDiscTest.php
index b051f8907..32f843174 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldDiscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldDiscTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class YieldDiscTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldMatTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldMatTest.php
index c6bc24fe9..28c554060 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldMatTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Financial/YieldMatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Financial;
 
 class YieldMatTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/FormulaArguments.php b/tests/PhpSpreadsheetTests/Calculation/Functions/FormulaArguments.php
index ac2324e82..13123dc15 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/FormulaArguments.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/FormulaArguments.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions;
 
 use PhpOffice\PhpSpreadsheet\Cell\CellAddress;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/DeprecatedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/DeprecatedFunctionsTest.php
index ca7c75d7d..864faf58a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/DeprecatedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/DeprecatedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/Div0Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/Div0Test.php
index 8655ff0b9..391b40380 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/Div0Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/Div0Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ErrorTypeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ErrorTypeTest.php
index f20cd94f6..c0e9eb4d0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ErrorTypeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ErrorTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsBlankTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsBlankTest.php
index f14ea6b1a..8a047a59e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsBlankTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsBlankTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrTest.php
index 00d5384b6..a24dde86f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrorTest.php
index 20eb04a9e..765cb8e55 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsEvenTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsEvenTest.php
index dd3871694..0ebf0ed05 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsEvenTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsEvenTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsFormulaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsFormulaTest.php
index 03e9bb70d..9f691d156 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsLogicalTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsLogicalTest.php
index 7b82440d0..ea53a56dc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsLogicalTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsLogicalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNaTest.php
index 51305209b..87e6be25b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNonTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNonTextTest.php
index 46513970e..e84c835cc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNonTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNonTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNumberTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNumberTest.php
index 860ccbf4a..91850022c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNumberTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsNumberTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsOddTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsOddTest.php
index 401f249f5..fb94d483c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsOddTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsOddTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsRefTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsRefTest.php
index c048d8c50..962e71fa9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsRefTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsRefTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsTextTest.php
index ec2663816..0fee579c0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/IsTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NTest.php
index 5aed21c4f..2224ad87a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\Value;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NaTest.php
index 471619f31..f8b8c92f4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NameTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NameTest.php
index 107e268c4..61953826a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NameTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NanTest.php
index 58f974888..f4e49ae55 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NullTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NullTest.php
index 65ce5ddbd..0a5d91eed 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NullTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/NullTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/RefTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/RefTest.php
index 7a8a33deb..d5b3df5e8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/RefTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/RefTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/TypeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/TypeTest.php
index 817abb4d8..4b36ccd6d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/TypeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/TypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\Value;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ValueTest.php
index 5ab07bd76..7aecf2d94 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Information/ValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Information;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AllSetupTeardown.php
index 1a14244df..8510d1ad2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AndTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AndTest.php
index ccc68c0ab..c9dacefd2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AndTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/AndTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class AndTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/DeprecatedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/DeprecatedFunctionsTest.php
index 11b1beaf9..4d0c1a814 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/DeprecatedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/DeprecatedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Logical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/FalseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/FalseTest.php
index e19ff3874..08ac289f0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/FalseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/FalseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class FalseTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfErrorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfErrorTest.php
index eae346775..6329c9b0e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfNaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfNaTest.php
index e31c9531b..a629bd7ab 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfNaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfNaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfTest.php
index bb9de92bc..fc631043a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class IfTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfsTest.php
index d52504643..eeb38b9a2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/IfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/NotTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/NotTest.php
index 9e2b825f2..db53b3894 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/NotTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/NotTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/OrTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/OrTest.php
index 8b7a48f18..6f369f573 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/OrTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/OrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class OrTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/SwitchTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/SwitchTest.php
index 2e923825c..1ef186060 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/SwitchTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/SwitchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/TrueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/TrueTest.php
index 5ce451702..0c61e4390 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/TrueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/TrueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class TrueTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/XorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/XorTest.php
index a41666987..e319cbb4a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/XorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Logical/XorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Logical;
 
 class XorTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressInternationalTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressInternationalTest.php
index 3f2539d20..da504e972 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressInternationalTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressInternationalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressTest.php
index aec33583b..0bb9833ab 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AddressTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AllSetupTeardown.php
index a6b500747..46947d7d1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ChooseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ChooseTest.php
index 22dc2626a..7a495a5ca 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ChooseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ChooseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnOnSpreadsheetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnOnSpreadsheetTest.php
index 29f49bc3a..de7a6cc22 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnOnSpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnOnSpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnTest.php
index d5e2c3ecc..9b007b0a9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\LookupRef;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsOnSpreadsheetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsOnSpreadsheetTest.php
index e1a80bcb3..76c866e5c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsOnSpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsOnSpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsTest.php
index 6ac932c85..641119a9d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/ColumnsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FilterTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FilterTest.php
index 5a584c464..ad0f4f0ee 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FilterTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FormulaTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FormulaTextTest.php
index cc1712e51..23a52cab3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FormulaTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/FormulaTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\LookupRef\Formula;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HLookupTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HLookupTest.php
index 0b04ca861..682a12e02 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HLookupTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HLookupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HyperlinkTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HyperlinkTest.php
index ab50f84e8..5eaf7d35e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HyperlinkTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/HyperlinkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexOnSpreadsheetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexOnSpreadsheetTest.php
index 651986932..e893fc7f3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexOnSpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexOnSpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 class IndexOnSpreadsheetTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexTest.php
index 9c9a675bb..9b3f5de2e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectInternationalTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectInternationalTest.php
index 881fb2f95..2c974282a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectInternationalTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectInternationalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectTest.php
index 39a3debcb..3ea20cac3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/IndirectTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\NamedFormula;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/LookupTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/LookupTest.php
index d0e56110a..7194fe380 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/LookupTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/LookupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatchTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatchTest.php
index f9c6ee13f..6a1c809f1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatchTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatrixHelperFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatrixHelperFunctionsTest.php
index 60952babd..62e3b0357 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatrixHelperFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MatrixHelperFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\LookupRef\Matrix;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MovedFunctionsTest.php
index 0f732306c..b96ad342c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/OffsetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/OffsetTest.php
index 4c644a489..2bf7f67bc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/OffsetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/OffsetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\LookupRef;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowOnSpreadsheetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowOnSpreadsheetTest.php
index 2216049fb..53fdbf087 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowOnSpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowOnSpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowTest.php
index 5c00cd821..fbc4c12d6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\LookupRef;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsOnSpreadsheetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsOnSpreadsheetTest.php
index 96c3304b7..5d21d9fc7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsOnSpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsOnSpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsTest.php
index 7acbbdbbb..11781aabc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/RowsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
index cad598e0b..99e0a6e45 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
index e57fee260..8334c20bf 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/TransposeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/TransposeTest.php
index 0c206f5d8..189269569 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/TransposeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/TransposeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/UniqueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/UniqueTest.php
index 44c071d2d..718fe2b8b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/UniqueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/UniqueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/VLookupTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/VLookupTest.php
index 66357d681..b898dbd5f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/VLookupTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/VLookupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\LookupRef;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AbsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AbsTest.php
index 98e95611f..e16a05d77 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AbsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AbsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcosTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcosTest.php
index 36f7bd9cf..8ba2e2a3a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcosTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcosTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcoshTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcoshTest.php
index 0dbe6ec7c..98ca3353c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcoshTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcoshTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcotTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcotTest.php
index 8f1b9a969..eabdd5115 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcotTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcotTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcothTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcothTest.php
index 5823945df..3935a32e9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcothTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AcothTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AllSetupTeardown.php
index ddd9c827e..8edba539f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ArabicTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ArabicTest.php
index a2621e817..d5fd394a7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ArabicTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ArabicTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinTest.php
index d0fde4a34..6024504c4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinhTest.php
index 908aa31fb..019ffb550 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AsinhTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Atan2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Atan2Test.php
index b08dcf63d..be37fdd24 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Atan2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Atan2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanTest.php
index 0cd7d7e10..d4156d6c2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanhTest.php
index 74d877902..0433535e3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/AtanhTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/BaseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/BaseTest.php
index 4be5c6f56..77b661c66 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/BaseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/BaseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingMathTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingMathTest.php
index 79b2f6385..384600d5b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingMathTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingMathTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingPreciseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingPreciseTest.php
index 7b6f0ef5c..d6e60e529 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingPreciseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingPreciseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingTest.php
index f193f91eb..ba246a03e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CeilingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinATest.php
index 7a615e97f..bc3d41ba8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinTest.php
index b622f96c5..6c4cdfa26 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CombinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CosTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CosTest.php
index 57275814c..0f5513d2d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CosTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CosTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CoshTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CoshTest.php
index c4f34b334..0239c1ee6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CoshTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CoshTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CotTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CotTest.php
index 6550f76c1..d7c71af59 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CotTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CotTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CothTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CothTest.php
index 501a9caee..1527ef764 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CothTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CothTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CscTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CscTest.php
index 76cb8e3f0..2b64c71a8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CscTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CscTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CschTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CschTest.php
index 901f317ef..9f2bf9050 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CschTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/CschTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/DegreesTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/DegreesTest.php
index 878fb832b..14d3d72bd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/DegreesTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/DegreesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/EvenTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/EvenTest.php
index ba7eb29af..88166169e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/EvenTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/EvenTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ExpTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ExpTest.php
index 433281f9d..7af6b3b09 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ExpTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ExpTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactDoubleTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactDoubleTest.php
index e2707de4b..e405c5d0f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactDoubleTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactDoubleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactTest.php
index 470a55491..1b1dbdb5c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FactTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php
index 7ade15040..f91076a23 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php
index 7f1fee280..3a43822e9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorTest.php
index 5ebadea1d..3d56fb328 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/GcdTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/GcdTest.php
index 31f3c1ce7..e7684ba14 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/GcdTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/GcdTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class GcdTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/IntTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/IntTest.php
index 7c8ad7e50..7f551e343 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/IntTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/IntTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LcmTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LcmTest.php
index ed5585a18..13d3b9940 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LcmTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LcmTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class LcmTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LnTest.php
index f362744b3..ca7eb78e8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Log10Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Log10Test.php
index 27d1fb98b..63ff4e952 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Log10Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/Log10Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LogTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LogTest.php
index 5f13f5b7f..69cd275be 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LogTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/LogTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MInverseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MInverseTest.php
index c3ccea802..63c118572 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MInverseTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MInverseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MMultTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MMultTest.php
index 1df9323de..86ee26fd9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MMultTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MMultTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MRoundTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MRoundTest.php
index ec22dfa18..520f6d50e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MRoundTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MRoundTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MUnitTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MUnitTest.php
index 9ac68ee5e..5d1abe126 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MUnitTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MUnitTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig\MatrixFunctions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MdeTermTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MdeTermTest.php
index 4e98e3026..8928f32c7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MdeTermTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MdeTermTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class MdeTermTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ModTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ModTest.php
index 526d7f241..f33b88650 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ModTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ModTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MovedFunctionsTest.php
index 646fd634b..91e0a92f8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MultinomialTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MultinomialTest.php
index 0cd8e7036..ce189b44e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MultinomialTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/MultinomialTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class MultinomialTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/OddTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/OddTest.php
index 7c9b26a49..de4522368 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/OddTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/OddTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/PowerTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/PowerTest.php
index 71021c58d..0bf42f09a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/PowerTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/PowerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ProductTest.php
index 5803fa237..7b4bc296e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/ProductTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class ProductTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/QuotientTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/QuotientTest.php
index 90478e6a0..84c2856be 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/QuotientTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/QuotientTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RadiansTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RadiansTest.php
index 4f9cca253..fb3c784eb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RadiansTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RadiansTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandArrayTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandArrayTest.php
index 6fffb31c7..3b5f73025 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandArrayTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandBetweenTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandBetweenTest.php
index 15184d3b8..059723616 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandBetweenTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandBetweenTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandTest.php
index 989c4883b..f1cd7cc70 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RandTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class RandTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RomanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RomanTest.php
index bbef39aae..1e536a11a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RomanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RomanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundDownTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundDownTest.php
index 6ba8ce3e0..b65da3627 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundDownTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundDownTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundTest.php
index 8a64fd764..b9d776242 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundUpTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundUpTest.php
index df2c76035..5ad00d36e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundUpTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/RoundUpTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SecTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SecTest.php
index 755c91485..4485b566f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SecTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SecTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SechTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SechTest.php
index 62245abc8..7605f95fc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SechTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SechTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SequenceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SequenceTest.php
index a3cd1c37a..4db230ece 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SequenceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SequenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\MathTrig\MatrixFunctions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SeriesSumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SeriesSumTest.php
index 2affa033a..8608f91c8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SeriesSumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SeriesSumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SignTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SignTest.php
index ed0721c59..436d0fe02 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SignTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SignTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinTest.php
index ff19bc421..83bc295f8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinhTest.php
index 03841b92b..0ad727757 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SinhTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtPiTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtPiTest.php
index ecad7bc3b..e6a1e783d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtPiTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtPiTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtTest.php
index 495d2f9bf..4bd348ffc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SqrtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SubTotalTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SubTotalTest.php
index c03bc1edf..b93b7f260 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SubTotalTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SubTotalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class SubTotalTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfTest.php
index 64f6795e6..1f61aa863 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class SumIfTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfsTest.php
index 42a7d7b93..eca29781f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumIfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumProductTest.php
index 24d3b3706..2158894b9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumProductTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumSqTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumSqTest.php
index 24754675b..41b3e4c61 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumSqTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumSqTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 class SumSqTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
index 761555d70..5c9bd238d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2MY2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2MY2Test.php
index d69697240..c7d1bf8c2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2MY2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2MY2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2PY2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2PY2Test.php
index 32a9d5776..b75ea02df 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2PY2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumX2PY2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumXMY2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumXMY2Test.php
index f3fee91cb..4cce0ada0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumXMY2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumXMY2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanTest.php
index aae1cf233..c21d451a1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanhTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanhTest.php
index 9c151b515..8de5d6803 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanhTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TanhTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
index cc5cd5891..beaf0a831 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/TruncTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AllSetupTeardown.php
index 49ad9da70..261ece097 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AveDevTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AveDevTest.php
index 159799c9b..ea9c61ef8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AveDevTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AveDevTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class AveDevTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageATest.php
index 3d0f38618..48788ab40 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class AverageATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIf2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIf2Test.php
index 1899239f8..4cbdee063 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIf2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIf2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfTest.php
index 558741245..2b23a77d2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfsTest.php
index d69622112..e3f835809 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageIfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageTest.php
index d5d313367..078a8313b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/AverageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class AverageTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaDistTest.php
index 986fd3d84..2a25cbfe6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaInvTest.php
index 284758543..eab0cf4ba 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BetaInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistRangeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistRangeTest.php
index 2b4bfe241..9a8ac452f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistTest.php
index 09179d31b..5f824d717 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomInvTest.php
index 01f4aea68..ecd12285c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/BinomInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistLeftTailTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistLeftTailTest.php
index f8865d6d9..a9319cee6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistLeftTailTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistLeftTailTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistRightTailTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistRightTailTest.php
index f4c52b116..94835eb61 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistRightTailTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiDistRightTailTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvLeftTailTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvLeftTailTest.php
index 4afea84ca..d12f3b3f4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvLeftTailTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvLeftTailTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvRightTailTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvRightTailTest.php
index 1125a8cac..82da0a6d6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvRightTailTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiInvRightTailTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiTestTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiTestTest.php
index 1a0be2d1b..0059a9de8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiTestTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ChiTestTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ConfidenceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ConfidenceTest.php
index bd8a09b3b..006ad32eb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ConfidenceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ConfidenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CorrelTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CorrelTest.php
index 3ed3b1f49..e832a89e7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CorrelTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CorrelTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountATest.php
index 241693c17..381b1384d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class CountATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountBlankTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountBlankTest.php
index fecc23eaa..e5f44f78d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountBlankTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountBlankTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfTest.php
index 45ab58d73..794751d6f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class CountIfTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfsTest.php
index f8b3d20a6..54c8a05be 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountIfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 // TODO There are some commented out cases which don't return correct value
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountTest.php
index 91ef6e2d4..ef951be3f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CountTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class CountTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CovarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CovarTest.php
index 02adef256..63b11e8d3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CovarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/CovarTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class CovarTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/DevSqTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/DevSqTest.php
index 28c01d68b..e239e105a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/DevSqTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/DevSqTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class DevSqTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ExponDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ExponDistTest.php
index f44235589..2cb5b64cb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ExponDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ExponDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FDistTest.php
index c77b22a05..6c6478f28 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherInvTest.php
index e036f4841..aa3189742 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherTest.php
index 144498023..352a3afc5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/FisherTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ForecastTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ForecastTest.php
index 5286f2dd9..396e69e0b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ForecastTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ForecastTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaDistTest.php
index 95cf51f5c..64ef50a5f 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaInvTest.php
index 6a1700e0e..b3d1a3409 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaLnTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaLnTest.php
index 16285b54a..8c9c4c76a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaLnTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaLnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaTest.php
index ead69416f..9db243cc0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GammaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GaussTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GaussTest.php
index ceffa9795..4fb98f5ec 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GaussTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GaussTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GeoMeanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GeoMeanTest.php
index dc58c2bb1..f5b8b91b4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GeoMeanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GeoMeanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class GeoMeanTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
index 7db793bbb..51d379a8d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/GrowthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HarMeanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HarMeanTest.php
index 80dc768df..497f8127c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HarMeanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HarMeanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class HarMeanTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HypGeomDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HypGeomDistTest.php
index b2ef0eb48..b240d874b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HypGeomDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/HypGeomDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/InterceptTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/InterceptTest.php
index 5ebdbeabd..c340c9899 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/InterceptTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/InterceptTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class InterceptTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/KurtTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/KurtTest.php
index c1604647c..1b2d79168 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/KurtTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/KurtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class KurtTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LargeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LargeTest.php
index 0586e066b..de1e4aa1e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LargeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LargeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class LargeTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LinEstTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LinEstTest.php
index 6b61dfd74..1c86b7128 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LinEstTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LinEstTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
index 3a5939681..9c1314eb7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogEstTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogInvTest.php
index 893235e3f..fce4a4b24 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDist2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDist2Test.php
index 265685caa..0857e5424 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDist2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDist2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDistTest.php
index 9f1770d7c..fcb01d5a4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/LogNormDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxATest.php
index d923d208e..4e65e2db4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MaxATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxIfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxIfsTest.php
index 8f77cb612..25a7ac696 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxIfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxIfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MaxIfsTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxTest.php
index 9c0cf948f..ea1e5110b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MaxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MaxTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MedianTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MedianTest.php
index 01d21c6ba..2eeaf6042 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MedianTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MedianTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MedianTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinATest.php
index 5701e6784..28d417dae 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MinATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinIfsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinIfsTest.php
index 7de8a723e..7fb91bfbc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinIfsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinIfsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MinIfsTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinTest.php
index 1f32bf466..c699cfedf 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class MinTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ModeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ModeTest.php
index e4dd6bf84..5ae2c4977 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ModeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ModeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MovedFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MovedFunctionsTest.php
index e51e8823f..6b0b8c628 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MovedFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/MovedFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NegBinomDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NegBinomDistTest.php
index 5768b331b..7725556ee 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NegBinomDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NegBinomDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormDistTest.php
index 6afe6c28a..ba62123ec 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormInvTest.php
index decd67665..5aa42fc85 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDist2Test.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDist2Test.php
index c4ae83155..c85c125c7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDist2Test.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDist2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDistTest.php
index df900c088..95d8ff32d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSInvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSInvTest.php
index c10eb1a14..e93553802 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSInvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/NormSInvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentRankTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentRankTest.php
index f5b8c2356..83b091fe2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentRankTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentRankTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class PercentRankTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentileTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentileTest.php
index 3d51e5323..47faff9e3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentileTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PercentileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class PercentileTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutTest.php
index 6fcbf499f..75a799956 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutationATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutationATest.php
index 2ae147bda..2cfc6a567 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutationATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PermutationATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PoissonTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PoissonTest.php
index 1b114c88d..2233a74ec 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PoissonTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/PoissonTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/QuartileTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/QuartileTest.php
index 5216aec16..daf658b84 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/QuartileTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/QuartileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class QuartileTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RankTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RankTest.php
index 6b0103420..5777a8f2d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RankTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RankTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class RankTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RsqTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RsqTest.php
index 7195c425f..fba99b1b8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RsqTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/RsqTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class RsqTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SkewTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SkewTest.php
index 11ff5abf6..f88287cc3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SkewTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SkewTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class SkewTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SlopeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SlopeTest.php
index 0c99e6e6e..12220561b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SlopeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SlopeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class SlopeTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SmallTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SmallTest.php
index 5b7e10877..13dc6f99c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SmallTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SmallTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class SmallTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevATest.php
index 12d5c1b47..c6964f948 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class StDevATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPATest.php
index b99842b78..db309b2f7 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class StDevPATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPTest.php
index 3f4b7e595..89898d2a1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevPTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class StDevPTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevTest.php
index 7b01080f4..b92062153 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StDevTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class StDevTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StandardizeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StandardizeTest.php
index 8614edad4..8defe4c03 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StandardizeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/StandardizeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SteyxTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SteyxTest.php
index 1e491f206..5c195630a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SteyxTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/SteyxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class SteyxTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TDistTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TDistTest.php
index fe12559d7..c57deb266 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TDistTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TDistTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TinvTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TinvTest.php
index dce482a86..ed16e9dba 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TinvTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TinvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
index 3a054b471..1a09ce9b4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrendTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Statistical;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrimMeanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrimMeanTest.php
index 72135e55d..1e6adfdcb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrimMeanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/TrimMeanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class TrimMeanTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarATest.php
index 5dfb9cdd3..084a452e4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class VarATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPATest.php
index ecad925da..9c1e62fdb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPATest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class VarPATest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPTest.php
index 9b68c3765..45f46d08b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarPTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class VarPTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarTest.php
index 0441df8ee..c565b4177 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/VarTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 class VarTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/WeibullTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/WeibullTest.php
index 8e415f5d8..533477525 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/WeibullTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/WeibullTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ZTestTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ZTestTest.php
index cf00346e5..32ae58a1c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ZTestTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Statistical/ZTestTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Statistical;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/AllSetupTeardown.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/AllSetupTeardown.php
index 80de252b4..e50b8163c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/AllSetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/AllSetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalcException;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
index a63bd6f24..56d035729 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ArrayToTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 class ArrayToTextTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharNonPrintableTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharNonPrintableTest.php
index 035cdfa0e..370ec308c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharNonPrintableTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharNonPrintableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharTest.php
index 7cd7e056b..e9549e452 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CharTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CleanTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CleanTest.php
index cf03876a4..7b83438cd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CleanTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CleanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CodeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CodeTest.php
index d753e78fc..e29c057a6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CodeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/CodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
index 9e9198e71..cfe566263 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DeprecatedTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DeprecatedTest.php
index 5ecd3f507..d6e50de05 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DeprecatedTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DeprecatedTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\TextData;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DollarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DollarTest.php
index 822dfbe5f..19c9dc3b6 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DollarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/DollarTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ExactTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ExactTest.php
index 4257f6da4..802b73e4c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ExactTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ExactTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FindTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FindTest.php
index 08f3bcfc9..6f5e187b8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FindTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FindTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FixedTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FixedTest.php
index 0a0242448..0ee5c1cc3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FixedTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/FixedTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LeftTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LeftTest.php
index c467b1cd6..4be89c238 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LeftTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LeftTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LenTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LenTest.php
index 9f8bd05fa..e2db773ae 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LenTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LenTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LowerTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LowerTest.php
index 2873c58dc..7549a3a4a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LowerTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/LowerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/MidTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/MidTest.php
index f8336ea6c..4a103f2bf 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/MidTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/MidTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/NumberValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/NumberValueTest.php
index 935ea0659..9dfa1fa20 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/NumberValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/NumberValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/OpenOfficeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/OpenOfficeTest.php
index afc8bf499..c7af96f64 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/OpenOfficeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/OpenOfficeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 class OpenOfficeTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ProperTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ProperTest.php
index 75e7c5a96..a3aee9143 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ProperTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ProperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReplaceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReplaceTest.php
index b3554f423..68a6f501e 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReplaceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReplaceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReptTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReptTest.php
index f483e4607..8cbed14d3 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReptTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ReptTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/RightTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/RightTest.php
index d3f5d212c..d2bc68362 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/RightTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/RightTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SearchTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SearchTest.php
index cb0e627f0..5c441b7dd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SearchTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SearchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SubstituteTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SubstituteTest.php
index 7c00c6229..927330252 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SubstituteTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/SubstituteTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TTest.php
index bf184d6b6..6f2bf123a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextAfterTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextAfterTest.php
index b64db024b..9f50af3ef 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextAfterTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextAfterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 class TextAfterTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextBeforeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextBeforeTest.php
index 6ee11bac4..05f0715ee 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextBeforeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextBeforeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 class TextBeforeTest extends AllSetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextJoinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextJoinTest.php
index 0a4de8420..e9a231a05 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextJoinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextJoinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextSplitTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextSplitTest.php
index e6c366770..9801d77d4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextSplitTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextSplitTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextTest.php
index 9c0cd97e9..eedd8b93b 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TrimTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TrimTest.php
index c4e2b7d6a..30929afd9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TrimTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/TrimTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/UpperTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/UpperTest.php
index 2ac7c9979..964a2accb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/UpperTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/UpperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
index b503846b7..a06fe6911 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueToTextTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueToTextTest.php
index ef6c41e97..9aa277e44 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueToTextTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueToTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
 use PhpOffice\PhpSpreadsheet\Calculation\TextData\Format;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Web/UrlEncodeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Web/UrlEncodeTest.php
index ea83d4369..8ab1337f1 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Web/UrlEncodeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Web/UrlEncodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Web;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Web\Service;
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Web/WebServiceTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Web/WebServiceTest.php
index f37bbd346..a5ef6e6cd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Web/WebServiceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Web/WebServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\Web;
 
 use PhpOffice\PhpSpreadsheet\Settings;
diff --git a/tests/PhpSpreadsheetTests/Calculation/FunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/FunctionsTest.php
index 0e0323a60..d4908ad5a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/FunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/FunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Calculation/MergedCellTest.php b/tests/PhpSpreadsheetTests/Calculation/MergedCellTest.php
index 036849295..efaefc9a0 100644
--- a/tests/PhpSpreadsheetTests/Calculation/MergedCellTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/MergedCellTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/NullEqualsZeroTest.php b/tests/PhpSpreadsheetTests/Calculation/NullEqualsZeroTest.php
index 0168e080d..c9b8409c2 100644
--- a/tests/PhpSpreadsheetTests/Calculation/NullEqualsZeroTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/NullEqualsZeroTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/ParseFormulaTest.php b/tests/PhpSpreadsheetTests/Calculation/ParseFormulaTest.php
index 06601abc0..c4958b5a9 100644
--- a/tests/PhpSpreadsheetTests/Calculation/ParseFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/ParseFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/RefErrorTest.php b/tests/PhpSpreadsheetTests/Calculation/RefErrorTest.php
index 78db701c1..657d79fbb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/RefErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/RefErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/RowColumnReferenceTest.php b/tests/PhpSpreadsheetTests/Calculation/RowColumnReferenceTest.php
index 1c28334bd..121958364 100644
--- a/tests/PhpSpreadsheetTests/Calculation/RowColumnReferenceTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/RowColumnReferenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Calculation/StringLengthTest.php b/tests/PhpSpreadsheetTests/Calculation/StringLengthTest.php
index 09f321188..33081e9aa 100644
--- a/tests/PhpSpreadsheetTests/Calculation/StringLengthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/StringLengthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Calculation/StructuredReferenceFormulaTest.php b/tests/PhpSpreadsheetTests/Calculation/StructuredReferenceFormulaTest.php
index 8d7977d43..b20c0985d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/StructuredReferenceFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/StructuredReferenceFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/PhpSpreadsheetTests/Calculation/TranslationTest.php b/tests/PhpSpreadsheetTests/Calculation/TranslationTest.php
index d01dde7ea..39fa96a65 100644
--- a/tests/PhpSpreadsheetTests/Calculation/TranslationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/TranslationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Calculation/XlfnFunctionsTest.php b/tests/PhpSpreadsheetTests/Calculation/XlfnFunctionsTest.php
index 3edd22c87..73d1af3cc 100644
--- a/tests/PhpSpreadsheetTests/Calculation/XlfnFunctionsTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/XlfnFunctionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Calculation;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Cell/AddressHelperTest.php b/tests/PhpSpreadsheetTests/Cell/AddressHelperTest.php
index 8ac5acc5e..7b41d8bd2 100644
--- a/tests/PhpSpreadsheetTests/Cell/AddressHelperTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/AddressHelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\AddressHelper;
diff --git a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
index 279699484..9963f01f6 100644
--- a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\AdvancedValueBinder;
diff --git a/tests/PhpSpreadsheetTests/Cell/CellAddressTest.php b/tests/PhpSpreadsheetTests/Cell/CellAddressTest.php
index 46a1b3f84..2cddc48a0 100644
--- a/tests/PhpSpreadsheetTests/Cell/CellAddressTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CellAddressTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\CellAddress;
diff --git a/tests/PhpSpreadsheetTests/Cell/CellDetachTest.php b/tests/PhpSpreadsheetTests/Cell/CellDetachTest.php
index 950322a7f..388d3ad71 100644
--- a/tests/PhpSpreadsheetTests/Cell/CellDetachTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CellDetachTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Cell/CellRangeTest.php b/tests/PhpSpreadsheetTests/Cell/CellRangeTest.php
index 1557a6982..8c8923ab3 100644
--- a/tests/PhpSpreadsheetTests/Cell/CellRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CellRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\CellAddress;
diff --git a/tests/PhpSpreadsheetTests/Cell/CellTest.php b/tests/PhpSpreadsheetTests/Cell/CellTest.php
index 76a14255a..fee24c78c 100644
--- a/tests/PhpSpreadsheetTests/Cell/CellTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CellTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\AdvancedValueBinder;
diff --git a/tests/PhpSpreadsheetTests/Cell/ColumnRangeTest.php b/tests/PhpSpreadsheetTests/Cell/ColumnRangeTest.php
index 14455701f..10da1dd21 100644
--- a/tests/PhpSpreadsheetTests/Cell/ColumnRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/ColumnRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\ColumnRange;
diff --git a/tests/PhpSpreadsheetTests/Cell/CoordinateTest.php b/tests/PhpSpreadsheetTests/Cell/CoordinateTest.php
index 5229a9cec..c67145b25 100644
--- a/tests/PhpSpreadsheetTests/Cell/CoordinateTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CoordinateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
diff --git a/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php b/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
index 2c591314b..974297c4c 100644
--- a/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Cell/DataValidationTest.php b/tests/PhpSpreadsheetTests/Cell/DataValidationTest.php
index 62be68dd2..cad9e6de8 100644
--- a/tests/PhpSpreadsheetTests/Cell/DataValidationTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/DataValidationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Cell/DataValidator2Test.php b/tests/PhpSpreadsheetTests/Cell/DataValidator2Test.php
index 9153a5b81..f16191a0f 100644
--- a/tests/PhpSpreadsheetTests/Cell/DataValidator2Test.php
+++ b/tests/PhpSpreadsheetTests/Cell/DataValidator2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Cell/DataValidatorTest.php b/tests/PhpSpreadsheetTests/Cell/DataValidatorTest.php
index bae315aff..679219710 100644
--- a/tests/PhpSpreadsheetTests/Cell/DataValidatorTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/DataValidatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Cell/DefaultValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/DefaultValueBinderTest.php
index 7e4332669..9057c2a31 100644
--- a/tests/PhpSpreadsheetTests/Cell/DefaultValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/DefaultValueBinderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Cell/HyperlinkTest.php b/tests/PhpSpreadsheetTests/Cell/HyperlinkTest.php
index e92fbaf3d..68d43e418 100644
--- a/tests/PhpSpreadsheetTests/Cell/HyperlinkTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/HyperlinkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\Hyperlink;
diff --git a/tests/PhpSpreadsheetTests/Cell/RowRangeTest.php b/tests/PhpSpreadsheetTests/Cell/RowRangeTest.php
index 32605cf07..52fd357f5 100644
--- a/tests/PhpSpreadsheetTests/Cell/RowRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/RowRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\RowRange;
diff --git a/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
index 6d6886484..192bcd388 100644
--- a/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Cell/ValueBinderWithOverriddenDataTypeForValue.php b/tests/PhpSpreadsheetTests/Cell/ValueBinderWithOverriddenDataTypeForValue.php
index e2ddc6023..ea4610e91 100644
--- a/tests/PhpSpreadsheetTests/Cell/ValueBinderWithOverriddenDataTypeForValue.php
+++ b/tests/PhpSpreadsheetTests/Cell/ValueBinderWithOverriddenDataTypeForValue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Cell;
 
 use PhpOffice\PhpSpreadsheet\Cell\DefaultValueBinder;
diff --git a/tests/PhpSpreadsheetTests/CellReferenceHelperTest.php b/tests/PhpSpreadsheetTests/CellReferenceHelperTest.php
index 8431a800f..572ffbff0 100644
--- a/tests/PhpSpreadsheetTests/CellReferenceHelperTest.php
+++ b/tests/PhpSpreadsheetTests/CellReferenceHelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\CellReferenceHelper;
diff --git a/tests/PhpSpreadsheetTests/Chart/AxisGlowTest.php b/tests/PhpSpreadsheetTests/Chart/AxisGlowTest.php
index b14d63fb7..2d42a4440 100644
--- a/tests/PhpSpreadsheetTests/Chart/AxisGlowTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/AxisGlowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/AxisPropertiesTest.php b/tests/PhpSpreadsheetTests/Chart/AxisPropertiesTest.php
index 59eaf494d..11c11660e 100644
--- a/tests/PhpSpreadsheetTests/Chart/AxisPropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/AxisPropertiesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/AxisShadowTest.php b/tests/PhpSpreadsheetTests/Chart/AxisShadowTest.php
index 78deece48..5a9b43265 100644
--- a/tests/PhpSpreadsheetTests/Chart/AxisShadowTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/AxisShadowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/BarChartCustomColorsTest.php b/tests/PhpSpreadsheetTests/Chart/BarChartCustomColorsTest.php
index 431ad670c..24fd0b0da 100644
--- a/tests/PhpSpreadsheetTests/Chart/BarChartCustomColorsTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/BarChartCustomColorsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/ChartBorderTest.php b/tests/PhpSpreadsheetTests/Chart/ChartBorderTest.php
index f5efc09f9..834c89c4a 100644
--- a/tests/PhpSpreadsheetTests/Chart/ChartBorderTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ChartBorderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Properties;
diff --git a/tests/PhpSpreadsheetTests/Chart/ChartMethodTest.php b/tests/PhpSpreadsheetTests/Chart/ChartMethodTest.php
index 5c3622ad4..a7ff421b3 100644
--- a/tests/PhpSpreadsheetTests/Chart/ChartMethodTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ChartMethodTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32CatAxValAxTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32CatAxValAxTest.php
index 458e8f272..083e9a6c3 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32CatAxValAxTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32CatAxValAxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32ColoredAxisLabelTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32ColoredAxisLabelTest.php
index f0c84bf0b..ec705f6ca 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32ColoredAxisLabelTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32ColoredAxisLabelTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32DsvGlowTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32DsvGlowTest.php
index 26ef34ee1..64e559d7d 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32DsvGlowTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32DsvGlowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32DsvLabelsTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32DsvLabelsTest.php
index b64907765..b53be9047 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32DsvLabelsTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32DsvLabelsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32ScatterTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32ScatterTest.php
index fcde7ae35..21999037c 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32ScatterTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32ScatterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\ChartColor;
diff --git a/tests/PhpSpreadsheetTests/Chart/Charts32XmlTest.php b/tests/PhpSpreadsheetTests/Chart/Charts32XmlTest.php
index e478b0f5c..d6b6564a0 100644
--- a/tests/PhpSpreadsheetTests/Chart/Charts32XmlTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/Charts32XmlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Properties;
diff --git a/tests/PhpSpreadsheetTests/Chart/ChartsOpenpyxlTest.php b/tests/PhpSpreadsheetTests/Chart/ChartsOpenpyxlTest.php
index e6f574fd3..706784185 100644
--- a/tests/PhpSpreadsheetTests/Chart/ChartsOpenpyxlTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ChartsOpenpyxlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/ChartsTitleTest.php b/tests/PhpSpreadsheetTests/Chart/ChartsTitleTest.php
index 5a929c628..ff6b6a1ea 100644
--- a/tests/PhpSpreadsheetTests/Chart/ChartsTitleTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ChartsTitleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Title;
diff --git a/tests/PhpSpreadsheetTests/Chart/ColorTest.php b/tests/PhpSpreadsheetTests/Chart/ColorTest.php
index e8326e523..62da8ef3a 100644
--- a/tests/PhpSpreadsheetTests/Chart/ColorTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ColorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\ChartColor;
diff --git a/tests/PhpSpreadsheetTests/Chart/DataSeriesColorTest.php b/tests/PhpSpreadsheetTests/Chart/DataSeriesColorTest.php
index c0b7069d8..690445d3e 100644
--- a/tests/PhpSpreadsheetTests/Chart/DataSeriesColorTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/DataSeriesColorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis as ChartAxis;
diff --git a/tests/PhpSpreadsheetTests/Chart/DataSeriesValues2Test.php b/tests/PhpSpreadsheetTests/Chart/DataSeriesValues2Test.php
index bba1c1f1b..a525322b2 100644
--- a/tests/PhpSpreadsheetTests/Chart/DataSeriesValues2Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/DataSeriesValues2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/DataSeriesValuesTest.php b/tests/PhpSpreadsheetTests/Chart/DataSeriesValuesTest.php
index 47c2fb895..58783bc1d 100644
--- a/tests/PhpSpreadsheetTests/Chart/DataSeriesValuesTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/DataSeriesValuesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\DataSeriesValues;
diff --git a/tests/PhpSpreadsheetTests/Chart/GridlinesLineStyleTest.php b/tests/PhpSpreadsheetTests/Chart/GridlinesLineStyleTest.php
index 49adf3cee..f4e011539 100644
--- a/tests/PhpSpreadsheetTests/Chart/GridlinesLineStyleTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/GridlinesLineStyleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/GridlinesShadowGlowTest.php b/tests/PhpSpreadsheetTests/Chart/GridlinesShadowGlowTest.php
index e12154413..908190bcb 100644
--- a/tests/PhpSpreadsheetTests/Chart/GridlinesShadowGlowTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/GridlinesShadowGlowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue2077Test.php b/tests/PhpSpreadsheetTests/Chart/Issue2077Test.php
index 2d1688c6b..520af8c27 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue2077Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue2077Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue2506Test.php b/tests/PhpSpreadsheetTests/Chart/Issue2506Test.php
index e1c307709..32a8fcee7 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue2506Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue2506Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue2931Test.php b/tests/PhpSpreadsheetTests/Chart/Issue2931Test.php
index 960eb04e8..2e1bd9d81 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue2931Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue2931Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue2965Test.php b/tests/PhpSpreadsheetTests/Chart/Issue2965Test.php
index 8294d39b6..90396e27f 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue2965Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue2965Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue3397Test.php b/tests/PhpSpreadsheetTests/Chart/Issue3397Test.php
index 85670976e..06b8189f4 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue3397Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue3397Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/Issue589Test.php b/tests/PhpSpreadsheetTests/Chart/Issue589Test.php
index 25fac07bc..7d1879ee2 100644
--- a/tests/PhpSpreadsheetTests/Chart/Issue589Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/Issue589Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Chart/LayoutEffectsTest.php b/tests/PhpSpreadsheetTests/Chart/LayoutEffectsTest.php
index 4c1bb9e5d..ca8070ae3 100644
--- a/tests/PhpSpreadsheetTests/Chart/LayoutEffectsTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/LayoutEffectsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/LayoutTest.php b/tests/PhpSpreadsheetTests/Chart/LayoutTest.php
index 5df139e3e..e54f1646b 100644
--- a/tests/PhpSpreadsheetTests/Chart/LayoutTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/LayoutTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\ChartColor;
diff --git a/tests/PhpSpreadsheetTests/Chart/LegendColorTest.php b/tests/PhpSpreadsheetTests/Chart/LegendColorTest.php
index 1bf5cb32e..7393aa7e6 100644
--- a/tests/PhpSpreadsheetTests/Chart/LegendColorTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/LegendColorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\AxisText;
diff --git a/tests/PhpSpreadsheetTests/Chart/LegendTest.php b/tests/PhpSpreadsheetTests/Chart/LegendTest.php
index e68145c07..7c4cdddfd 100644
--- a/tests/PhpSpreadsheetTests/Chart/LegendTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/LegendTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Legend;
diff --git a/tests/PhpSpreadsheetTests/Chart/LineStylesTest.php b/tests/PhpSpreadsheetTests/Chart/LineStylesTest.php
index ef940c994..b382c4a92 100644
--- a/tests/PhpSpreadsheetTests/Chart/LineStylesTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/LineStylesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\GridLines;
diff --git a/tests/PhpSpreadsheetTests/Chart/MultiplierTest.php b/tests/PhpSpreadsheetTests/Chart/MultiplierTest.php
index c819e4733..72a02d5ad 100644
--- a/tests/PhpSpreadsheetTests/Chart/MultiplierTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/MultiplierTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/PR3163Test.php b/tests/PhpSpreadsheetTests/Chart/PR3163Test.php
index 154bc18da..bfce4ca8d 100644
--- a/tests/PhpSpreadsheetTests/Chart/PR3163Test.php
+++ b/tests/PhpSpreadsheetTests/Chart/PR3163Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/PieFillTest.php b/tests/PhpSpreadsheetTests/Chart/PieFillTest.php
index 5b35ca3d2..7a501efb0 100644
--- a/tests/PhpSpreadsheetTests/Chart/PieFillTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/PieFillTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/RenderTest.php b/tests/PhpSpreadsheetTests/Chart/RenderTest.php
index b10e854f9..fe1a0c1eb 100644
--- a/tests/PhpSpreadsheetTests/Chart/RenderTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/RenderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Chart;
diff --git a/tests/PhpSpreadsheetTests/Chart/RoundedCornersTest.php b/tests/PhpSpreadsheetTests/Chart/RoundedCornersTest.php
index 93bbaa231..8796451dc 100644
--- a/tests/PhpSpreadsheetTests/Chart/RoundedCornersTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/RoundedCornersTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Chart/ShadowPresetsTest.php b/tests/PhpSpreadsheetTests/Chart/ShadowPresetsTest.php
index 20cacbc17..5da26502c 100644
--- a/tests/PhpSpreadsheetTests/Chart/ShadowPresetsTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/ShadowPresetsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Axis;
diff --git a/tests/PhpSpreadsheetTests/Chart/TitleTest.php b/tests/PhpSpreadsheetTests/Chart/TitleTest.php
index 4c01d5fec..6d1507acd 100644
--- a/tests/PhpSpreadsheetTests/Chart/TitleTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/TitleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Chart\Title;
diff --git a/tests/PhpSpreadsheetTests/Chart/TrendLineTest.php b/tests/PhpSpreadsheetTests/Chart/TrendLineTest.php
index 954a73368..59c01d395 100644
--- a/tests/PhpSpreadsheetTests/Chart/TrendLineTest.php
+++ b/tests/PhpSpreadsheetTests/Chart/TrendLineTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Chart;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Collection/CellsTest.php b/tests/PhpSpreadsheetTests/Collection/CellsTest.php
index 9a59458ae..46f8755e0 100644
--- a/tests/PhpSpreadsheetTests/Collection/CellsTest.php
+++ b/tests/PhpSpreadsheetTests/Collection/CellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Collection;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/CommentTest.php b/tests/PhpSpreadsheetTests/CommentTest.php
index f2e0c2993..86a8825d6 100644
--- a/tests/PhpSpreadsheetTests/CommentTest.php
+++ b/tests/PhpSpreadsheetTests/CommentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Comment;
diff --git a/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php b/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
index fac233c8e..e7df5a667 100644
--- a/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
+++ b/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Custom;
 
 use Complex\Complex;
diff --git a/tests/PhpSpreadsheetTests/DefinedNameFormulaTest.php b/tests/PhpSpreadsheetTests/DefinedNameFormulaTest.php
index e1a9c2e69..131163def 100644
--- a/tests/PhpSpreadsheetTests/DefinedNameFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/DefinedNameFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\DefinedName;
diff --git a/tests/PhpSpreadsheetTests/DefinedNameTest.php b/tests/PhpSpreadsheetTests/DefinedNameTest.php
index c001f204e..e1a9bfe5d 100644
--- a/tests/PhpSpreadsheetTests/DefinedNameTest.php
+++ b/tests/PhpSpreadsheetTests/DefinedNameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\DefinedName;
diff --git a/tests/PhpSpreadsheetTests/Document/EpochTest.php b/tests/PhpSpreadsheetTests/Document/EpochTest.php
index d9a0e1efe..feb98c8af 100644
--- a/tests/PhpSpreadsheetTests/Document/EpochTest.php
+++ b/tests/PhpSpreadsheetTests/Document/EpochTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Document;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Document/PropertiesTest.php b/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
index 5b8604973..12de9c122 100644
--- a/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Document;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Document/SecurityTest.php b/tests/PhpSpreadsheetTests/Document/SecurityTest.php
index 959962603..015e32ba2 100644
--- a/tests/PhpSpreadsheetTests/Document/SecurityTest.php
+++ b/tests/PhpSpreadsheetTests/Document/SecurityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Document;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/DocumentGeneratorTest.php b/tests/PhpSpreadsheetTests/DocumentGeneratorTest.php
index 20d023ea7..ef1d3d352 100644
--- a/tests/PhpSpreadsheetTests/DocumentGeneratorTest.php
+++ b/tests/PhpSpreadsheetTests/DocumentGeneratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Category as Cat;
diff --git a/tests/PhpSpreadsheetTests/Features/AutoFilter/Xlsx/BasicLoadTest.php b/tests/PhpSpreadsheetTests/Features/AutoFilter/Xlsx/BasicLoadTest.php
index 63c3c6fd2..6131085b7 100644
--- a/tests/PhpSpreadsheetTests/Features/AutoFilter/Xlsx/BasicLoadTest.php
+++ b/tests/PhpSpreadsheetTests/Features/AutoFilter/Xlsx/BasicLoadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Features\AutoFilter\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Functional/AbstractFunctional.php b/tests/PhpSpreadsheetTests/Functional/AbstractFunctional.php
index 0587e3894..441e61e6d 100644
--- a/tests/PhpSpreadsheetTests/Functional/AbstractFunctional.php
+++ b/tests/PhpSpreadsheetTests/Functional/AbstractFunctional.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Functional/ActiveSheetTest.php b/tests/PhpSpreadsheetTests/Functional/ActiveSheetTest.php
index 7847e7365..a6e1b33ff 100644
--- a/tests/PhpSpreadsheetTests/Functional/ActiveSheetTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ActiveSheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/ColumnWidthTest.php b/tests/PhpSpreadsheetTests/Functional/ColumnWidthTest.php
index 18d4e4b6d..fa6e958f2 100644
--- a/tests/PhpSpreadsheetTests/Functional/ColumnWidthTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ColumnWidthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/CommentsTest.php b/tests/PhpSpreadsheetTests/Functional/CommentsTest.php
index dcaf1d361..36ec29b97 100644
--- a/tests/PhpSpreadsheetTests/Functional/CommentsTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/CommentsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/ConditionalStopIfTrueTest.php b/tests/PhpSpreadsheetTests/Functional/ConditionalStopIfTrueTest.php
index 991f5da94..06f4afe0c 100644
--- a/tests/PhpSpreadsheetTests/Functional/ConditionalStopIfTrueTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ConditionalStopIfTrueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/ConditionalTextTest.php b/tests/PhpSpreadsheetTests/Functional/ConditionalTextTest.php
index c8db3bf09..de8c47e80 100644
--- a/tests/PhpSpreadsheetTests/Functional/ConditionalTextTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ConditionalTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/DrawingImageHyperlinkTest.php b/tests/PhpSpreadsheetTests/Functional/DrawingImageHyperlinkTest.php
index be350ceda..711f87e24 100644
--- a/tests/PhpSpreadsheetTests/Functional/DrawingImageHyperlinkTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/DrawingImageHyperlinkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Cell\Hyperlink;
diff --git a/tests/PhpSpreadsheetTests/Functional/EnclosureTest.php b/tests/PhpSpreadsheetTests/Functional/EnclosureTest.php
index bbf54a2cf..c1b767192 100644
--- a/tests/PhpSpreadsheetTests/Functional/EnclosureTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/EnclosureTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/FreezePaneTest.php b/tests/PhpSpreadsheetTests/Functional/FreezePaneTest.php
index 1f7430e46..72e9ad1aa 100644
--- a/tests/PhpSpreadsheetTests/Functional/FreezePaneTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/FreezePaneTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/MergedCellsTest.php b/tests/PhpSpreadsheetTests/Functional/MergedCellsTest.php
index ce9493d17..c99826bfd 100644
--- a/tests/PhpSpreadsheetTests/Functional/MergedCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/MergedCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/PrintAreaTest.php b/tests/PhpSpreadsheetTests/Functional/PrintAreaTest.php
index 39f6517a5..535f927fe 100644
--- a/tests/PhpSpreadsheetTests/Functional/PrintAreaTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/PrintAreaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Reader\BaseReader;
diff --git a/tests/PhpSpreadsheetTests/Functional/ReadBlankCellsTest.php b/tests/PhpSpreadsheetTests/Functional/ReadBlankCellsTest.php
index 5384c254a..ad1729b00 100644
--- a/tests/PhpSpreadsheetTests/Functional/ReadBlankCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ReadBlankCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/ReadFilterFilter.php b/tests/PhpSpreadsheetTests/Functional/ReadFilterFilter.php
index a96dfd183..755ee2d34 100644
--- a/tests/PhpSpreadsheetTests/Functional/ReadFilterFilter.php
+++ b/tests/PhpSpreadsheetTests/Functional/ReadFilterFilter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Functional/ReadFilterTest.php b/tests/PhpSpreadsheetTests/Functional/ReadFilterTest.php
index c8fb1628a..75c8206d0 100644
--- a/tests/PhpSpreadsheetTests/Functional/ReadFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/ReadFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/SelectedCellsTest.php b/tests/PhpSpreadsheetTests/Functional/SelectedCellsTest.php
index e03b2a87d..89a7327e5 100644
--- a/tests/PhpSpreadsheetTests/Functional/SelectedCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/SelectedCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Functional/StreamTest.php b/tests/PhpSpreadsheetTests/Functional/StreamTest.php
index e0a4b27d6..3430b7a31 100644
--- a/tests/PhpSpreadsheetTests/Functional/StreamTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/StreamTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Functional/TypeAttributePreservationTest.php b/tests/PhpSpreadsheetTests/Functional/TypeAttributePreservationTest.php
index b852a879c..e90cf4267 100644
--- a/tests/PhpSpreadsheetTests/Functional/TypeAttributePreservationTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/TypeAttributePreservationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods as ReaderOds;
diff --git a/tests/PhpSpreadsheetTests/Functional/WorkbookViewAttributesTest.php b/tests/PhpSpreadsheetTests/Functional/WorkbookViewAttributesTest.php
index 698673fc7..5c21443a9 100644
--- a/tests/PhpSpreadsheetTests/Functional/WorkbookViewAttributesTest.php
+++ b/tests/PhpSpreadsheetTests/Functional/WorkbookViewAttributesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Functional;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/HashTableTest.php b/tests/PhpSpreadsheetTests/HashTableTest.php
index e40cf0fcd..086ee6f05 100644
--- a/tests/PhpSpreadsheetTests/HashTableTest.php
+++ b/tests/PhpSpreadsheetTests/HashTableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Comment; // need Comparable object
diff --git a/tests/PhpSpreadsheetTests/Helper/DimensionTest.php b/tests/PhpSpreadsheetTests/Helper/DimensionTest.php
index 5fdc3b75e..e6a823c76 100644
--- a/tests/PhpSpreadsheetTests/Helper/DimensionTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/DimensionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Helper;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Helper/HandlerTest.php b/tests/PhpSpreadsheetTests/Helper/HandlerTest.php
index 8eee3064f..bb8bf751f 100644
--- a/tests/PhpSpreadsheetTests/Helper/HandlerTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/HandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Helper;
 
 use PhpOffice\PhpSpreadsheet\Helper\Handler;
diff --git a/tests/PhpSpreadsheetTests/Helper/HtmlTest.php b/tests/PhpSpreadsheetTests/Helper/HtmlTest.php
index 8c9d7f5a6..8fb6c3b3d 100644
--- a/tests/PhpSpreadsheetTests/Helper/HtmlTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/HtmlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Helper;
 
 use PhpOffice\PhpSpreadsheet\Helper\Html;
diff --git a/tests/PhpSpreadsheetTests/Helper/SampleCoverageTest.php b/tests/PhpSpreadsheetTests/Helper/SampleCoverageTest.php
index f3f616fe6..2c54dd68f 100644
--- a/tests/PhpSpreadsheetTests/Helper/SampleCoverageTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/SampleCoverageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Helper;
 
 use PhpOffice\PhpSpreadsheet\Helper\Sample;
diff --git a/tests/PhpSpreadsheetTests/Helper/SampleTest.php b/tests/PhpSpreadsheetTests/Helper/SampleTest.php
index 387597f7d..7ec3b37bf 100644
--- a/tests/PhpSpreadsheetTests/Helper/SampleTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/SampleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Helper;
 
 use PhpOffice\PhpSpreadsheet\Helper\Sample;
diff --git a/tests/PhpSpreadsheetTests/IOFactoryTest.php b/tests/PhpSpreadsheetTests/IOFactoryTest.php
index 558766724..bf894c566 100644
--- a/tests/PhpSpreadsheetTests/IOFactoryTest.php
+++ b/tests/PhpSpreadsheetTests/IOFactoryTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/NamedFormulaTest.php b/tests/PhpSpreadsheetTests/NamedFormulaTest.php
index 28857abe6..2feec4dec 100644
--- a/tests/PhpSpreadsheetTests/NamedFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/NamedFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\NamedFormula;
diff --git a/tests/PhpSpreadsheetTests/NamedRange2Test.php b/tests/PhpSpreadsheetTests/NamedRange2Test.php
index 9303c9afb..6c20e145d 100644
--- a/tests/PhpSpreadsheetTests/NamedRange2Test.php
+++ b/tests/PhpSpreadsheetTests/NamedRange2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\DefinedName;
diff --git a/tests/PhpSpreadsheetTests/NamedRangeTest.php b/tests/PhpSpreadsheetTests/NamedRangeTest.php
index 9440ef21e..ffdfe5048 100644
--- a/tests/PhpSpreadsheetTests/NamedRangeTest.php
+++ b/tests/PhpSpreadsheetTests/NamedRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Reader/BaseNoLoad.php b/tests/PhpSpreadsheetTests/Reader/BaseNoLoad.php
index 02298e8d9..9655dc596 100644
--- a/tests/PhpSpreadsheetTests/Reader/BaseNoLoad.php
+++ b/tests/PhpSpreadsheetTests/Reader/BaseNoLoad.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader;
 
 use PhpOffice\PhpSpreadsheet\Reader\BaseReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/BaseNoLoadTest.php b/tests/PhpSpreadsheetTests/Reader/BaseNoLoadTest.php
index c79bb9e91..473aa6d66 100644
--- a/tests/PhpSpreadsheetTests/Reader/BaseNoLoadTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/BaseNoLoadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvCallbackTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvCallbackTest.php
index 3968c47de..6c28cb71e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvCallbackTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvCallbackTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousFilter.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousFilter.php
index 30b37051d..7ee93665e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousFilter.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousFilter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousTest.php
index 8c28c1e70..abb85d73e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvContiguousTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvEncodingTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvEncodingTest.php
index db8a46a55..2aeffa354 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvEncodingTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvEncodingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2232Test.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2232Test.php
index 4f1e95a54..ae305d42f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2232Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2232Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2840Test.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2840Test.php
index 760006835..48e9027a9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2840Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvIssue2840Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvLineEndingTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvLineEndingTest.php
index 1ac17b981..64dd48cb5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvLineEndingTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvLineEndingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvLoadFromStringTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvLoadFromStringTest.php
index f0ebf8d32..a485db93b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvLoadFromStringTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvLoadFromStringTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
index 70cfb39de..0da49772e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatTest.php
index 50047f374..3cf404709 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvTest.php
index cd8ece9b2..3f4375df8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/AutoFilterTest.php
index fd309fbd9..be82e77f3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/AutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Reader\Gnumeric;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericFilter.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericFilter.php
index 7e9090ce0..b33bb086f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericFilter.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericFilter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericInfoTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericInfoTest.php
index 7bc007763..74b9a8bde 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericInfoTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericInfoTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericLoadTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericLoadTest.php
index c413b3a74..e5e3a57e3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericLoadTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericLoadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use DateTimeZone;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericStylesTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericStylesTest.php
index 931fbc40c..e8d332895 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericStylesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/GnumericStylesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/HiddenWorksheetTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/HiddenWorksheetTest.php
index 611070218..021ece1cb 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/HiddenWorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/HiddenWorksheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Reader\Gnumeric;
diff --git a/tests/PhpSpreadsheetTests/Reader/Gnumeric/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Gnumeric/PageSetupTest.php
index bac8f4250..16a470810 100644
--- a/tests/PhpSpreadsheetTests/Reader/Gnumeric/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Gnumeric/PageSetupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Gnumeric;
 
 use PhpOffice\PhpSpreadsheet\Reader\Gnumeric;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlBorderTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlBorderTest.php
index c60fea5b7..a525b321a 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlBorderTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlBorderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlHelper.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlHelper.php
index a6be40c92..78986c8ca 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlHelper.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlHelper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlImageTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlImageTest.php
index fe0117cac..b56a316a1 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlImageTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlImageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Drawing;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php
index d5f5044aa..b943d1acd 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
index 5fa7ccf43..b567173d4 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php
index fce30b121..9a8f53a3e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTagsTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTagsTest.php
index 45a098a34..b4e248436 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTagsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTagsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
index a15b16cb4..afb01cbfe 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/Issue2029Test.php b/tests/PhpSpreadsheetTests/Reader/Html/Issue2029Test.php
index d30793504..76b647783 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/Issue2029Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/Issue2029Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
@@ -57,43 +59,43 @@ class Issue2029Test extends TestCase
                   </th>
                   <th class="text-center">
                       Apellido y Nombre
-                  </th>                        
+                  </th>
                   <th class="text-center">
                       Obra Social
                   </th>
                   <th class="text-center">
                     Corresponde Reducci&oacute;n?
-                  </th>                        
+                  </th>
                 </tr>
-                
+
                 <tr>
                     <td class="text-center">
                       12345678901
                     </td>
                     <td class="text-center">
                       EMILIANO ZAPATA SALAZAR
-                    </td>                        
+                    </td>
                     <td class="text-center">
                       101208
                     </td>
                     <td class="text-center">
                       Yes
-                    </td>                        
+                    </td>
                 </tr>
-                
+
                 <tr>
                     <td class="text-center">
                       23456789012
                     </td>
                     <td class="text-center">
                       FRANCISCO PANCHO VILLA
-                    </td>                        
+                    </td>
                     <td class="text-center">
                       101208
                     </td>
                     <td class="text-center">
                       No
-                    </td>                        
+                    </td>
                 </tr>
               </table>
             </body>
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/Issue2810Test.php b/tests/PhpSpreadsheetTests/Reader/Html/Issue2810Test.php
index 5e6e73869..b2ade3d5f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/Issue2810Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/Issue2810Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/Issue2942Test.php b/tests/PhpSpreadsheetTests/Reader/Html/Issue2942Test.php
index 3a41805c9..4b253c7ac 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/Issue2942Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/Issue2942Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Html;
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/ViewportTest.php b/tests/PhpSpreadsheetTests/Reader/Html/ViewportTest.php
index 1a167455a..fb9e3e9c9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/ViewportTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/ViewportTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
 
 use PhpOffice\PhpSpreadsheet\Document\Properties;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/AutoFilterTest.php
index 1fd709cac..2f1d1a411 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/AutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/DefinedNamesTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/DefinedNamesTest.php
index e93be4945..d5a572f77 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/DefinedNamesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/DefinedNamesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/EmptyFileTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/EmptyFileTest.php
index 5876eaab1..9e7c15515 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/EmptyFileTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/EmptyFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/HiddenMergeCellsTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/HiddenMergeCellsTest.php
index 3f38631c4..6612355b7 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/HiddenMergeCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/HiddenMergeCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/HiddenWorksheetTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/HiddenWorksheetTest.php
index 70b5d4b90..9793a3c09 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/HiddenWorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/HiddenWorksheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/HyperlinkTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/HyperlinkTest.php
index 2dc5f9cfa..c4bbef0ec 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/HyperlinkTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/HyperlinkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/InvalidFileTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/InvalidFileTest.php
index d56af4ded..550763756 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/InvalidFileTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/InvalidFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/Issue2810Test.php b/tests/PhpSpreadsheetTests/Reader/Ods/Issue2810Test.php
index bbb697b8a..7677e43a9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/Issue2810Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/Issue2810Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/MergeRangeTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/MergeRangeTest.php
index 5c36c65b8..a175c6f03 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/MergeRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/MergeRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/OdsInfoTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/OdsInfoTest.php
index 1de4252f8..e780d32b6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/OdsInfoTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/OdsInfoTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/OdsPropertiesTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/OdsPropertiesTest.php
index 3ba99e52b..8c1aff9b6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/OdsPropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/OdsPropertiesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Document\Properties;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/OdsTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/OdsTest.php
index 6e05709e9..684af4fd8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/OdsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/OdsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupBug1772Test.php b/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupBug1772Test.php
index 7fc7e5376..568bb602c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupBug1772Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupBug1772Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupTest.php
index 0ee190da5..227a11c6e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/PageSetupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\Ods;
diff --git a/tests/PhpSpreadsheetTests/Reader/Ods/RepeatedColumnsTest.php b/tests/PhpSpreadsheetTests/Reader/Ods/RepeatedColumnsTest.php
index 14309afa6..7b6e9dbb5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Ods/RepeatedColumnsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Ods/RepeatedColumnsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Ods;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php b/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
index 6570bf9b1..8215b8781 100644
--- a/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Security;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Slk/SlkCommentsTest.php b/tests/PhpSpreadsheetTests/Reader/Slk/SlkCommentsTest.php
index 6f8a7ef51..f77bc86d2 100644
--- a/tests/PhpSpreadsheetTests/Reader/Slk/SlkCommentsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Slk/SlkCommentsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Slk;
 
 use PhpOffice\PhpSpreadsheet\Reader\Slk;
diff --git a/tests/PhpSpreadsheetTests/Reader/Slk/SlkTest.php b/tests/PhpSpreadsheetTests/Reader/Slk/SlkTest.php
index 3a7dff6c4..c6820a873 100644
--- a/tests/PhpSpreadsheetTests/Reader/Slk/SlkTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Slk/SlkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Slk;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Utility/File.php b/tests/PhpSpreadsheetTests/Reader/Utility/File.php
index f2283326e..0290617b5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Utility/File.php
+++ b/tests/PhpSpreadsheetTests/Reader/Utility/File.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Utility;
 
 class File
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ColorMapTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ColorMapTest.php
index bd1cfa4c7..ee571b956 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ColorMapTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ColorMapTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls\Color\BIFF5;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ColourTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ColourTest.php
index d17e7e167..9b997ed8c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ColourTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ColourTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
index e399c6d81..684c3d263 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
index 0f683be26..abdfb9088 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
index 0c9f51ce7..80619af99 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/DefinedNameTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/DefinedNameTest.php
index c95615808..05290bd84 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/DefinedNameTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/DefinedNameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ErrorCodeMapTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ErrorCodeMapTest.php
index 251b37ea0..e9c82ffa7 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ErrorCodeMapTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ErrorCodeMapTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls\ErrorCode;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php
index 1617f89d7..86e551ba3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenMergeCellsTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenMergeCellsTest.php
index 0a59b7d44..7300c7ec9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenMergeCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenMergeCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
index aa50599c3..904843923 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/InfoNamesTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/InfoNamesTest.php
index a493d65be..4f9073a7b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/InfoNamesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/InfoNamesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/Issue2463Test.php b/tests/PhpSpreadsheetTests/Reader/Xls/Issue2463Test.php
index 902424fc7..9de1c4ba9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/Issue2463Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/Issue2463Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/Md5Test.php b/tests/PhpSpreadsheetTests/Reader/Xls/Md5Test.php
index f86d1c553..550f12767 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/Md5Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/Md5Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls\MD5;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/NonExistentFileTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/NonExistentFileTest.php
index 76db7b62a..f923a01f5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/NonExistentFileTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/NonExistentFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/NumberFormatGeneralTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/NumberFormatGeneralTest.php
index 3bfea8bf2..15711cad8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/NumberFormatGeneralTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/NumberFormatGeneralTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/PageBreakTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/PageBreakTest.php
index 6a2bd4091..475b4d83e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/PageBreakTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/PageBreakTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
index f90595465..2eb2bc633 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/Rc4Test.php b/tests/PhpSpreadsheetTests/Reader/Xls/Rc4Test.php
index c3056c08b..453ff2b5e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/Rc4Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/Rc4Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls\RC4;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/RichTextSizeTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/RichTextSizeTest.php
index cf45dec1a..39f2edd79 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/RichTextSizeTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/RichTextSizeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/SheetProtectionTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/SheetProtectionTest.php
index e6f827719..c6d040eb8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/SheetProtectionTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/SheetProtectionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/XlsTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/XlsTest.php
index 03c3afd4c..4cdfc06f6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/XlsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/XlsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/AbsolutePathTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/AbsolutePathTest.php
index 6a886abb4..a99eab803 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/AbsolutePathTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/AbsolutePathTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilter2Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilter2Test.php
index 7a2643948..be67423f8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilter2Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilter2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterEvaluateTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterEvaluateTest.php
index cb54c567e..70f332a16 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterEvaluateTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterEvaluateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterTest.php
index 7c75469f1..276a3e4fb 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/AutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx\AutoFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ChartSheetTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ChartSheetTest.php
index e7862697e..e433f01aa 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ChartSheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ChartSheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php
index 2218ace14..d16adeb99 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ColorTabTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/CommentTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/CommentTest.php
index cb7635e9e..1eb9eca01 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/CommentTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/CommentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/CondNumFmtTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/CondNumFmtTest.php
index 350baa76b..6797c7afa 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/CondNumFmtTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/CondNumFmtTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalBorderTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalBorderTest.php
index df5ebe64a..1d65d720c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalBorderTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalBorderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalFormattingDataBarXlsxTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalFormattingDataBarXlsxTest.php
index 0ec25d8e7..6a0ac7def 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalFormattingDataBarXlsxTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalFormattingDataBarXlsxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalNoFormatSetTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalNoFormatSetTest.php
index 570a613ea..86729c1c0 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalNoFormatSetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalNoFormatSetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalTest.php
index 29f0c5543..15af02dff 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ConditionalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php
index 6630a3fe6..8d6e6137e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/CoverageGapsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationBooleanValue.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationBooleanValue.php
index 34ac21124..16b6eb663 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationBooleanValue.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationBooleanValue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationTest.php
index ebd0b58ac..3de53c7c7 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DataValidationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFillTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFillTest.php
index dc61b9538..44fb8e57d 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFillTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFillTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFontTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFontTest.php
index a4e94804b..d000e3676 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFontTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DefaultFontTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DirectorySeparatorTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DirectorySeparatorTest.php
index e66c99e86..e90d599a1 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DirectorySeparatorTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DirectorySeparatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/DrawingOneCellAnchorTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/DrawingOneCellAnchorTest.php
index fe6b80786..b12b52e08 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/DrawingOneCellAnchorTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/DrawingOneCellAnchorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/EmptyFileTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/EmptyFileTest.php
index a2e78da4a..2136b3a7a 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/EmptyFileTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/EmptyFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
index 4f13264ff..919e617aa 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenMergeCellsTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenMergeCellsTest.php
index 9d4fc8180..334a6d929 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenMergeCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenMergeCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenWorksheetTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenWorksheetTest.php
index e11954eb5..b464cb6cf 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenWorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/HiddenWorksheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/HyperlinkTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/HyperlinkTest.php
index 81be815fa..81bc5e178 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/HyperlinkTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/HyperlinkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/IgnoredErrorTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/IgnoredErrorTest.php
index bb476d6d6..aa0cbbc4b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/IgnoredErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/IgnoredErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/InvalidFileTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/InvalidFileTest.php
index 05acd8743..95f49440b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/InvalidFileTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/InvalidFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue1482Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue1482Test.php
index 52536fc4c..e1d087550 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue1482Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue1482Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2301Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2301Test.php
index 7a5829f74..1d876a0ff 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2301Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2301Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2331Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2331Test.php
index afa2ff524..690c4e6f3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2331Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2331Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use DateTimeZone;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2362Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2362Test.php
index 7efb04ad2..85e11a357 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2362Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2362Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php
index 7e59418ad..c4ac64c39 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2387Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2450Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2450Test.php
index e6cb741bf..4ec43f574 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2450Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2450Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2488Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2488Test.php
index 9b77df4ef..6595cb5b4 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2488Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2488Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2490Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2490Test.php
index f65185e73..8307ce1db 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2490Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2490Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2494Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2494Test.php
index ff400264f..b691acd37 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2494Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2494Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2501Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2501Test.php
index 579582456..011d00b8f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2501Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2501Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2516Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2516Test.php
index 13725418a..e091d2a79 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2516Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2516Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2542Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2542Test.php
index ad9700014..34027522f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2542Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2542Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2778Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2778Test.php
index 925b6fa4f..b672f9c1c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2778Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2778Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2885Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2885Test.php
index 82727ef87..9f2783ce8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2885Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2885Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3126Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3126Test.php
index 2b8a5da70..8a1d3d7d1 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3126Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3126Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3145Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3145Test.php
index b7d3a4cc7..df56d44bc 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3145Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3145Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3277Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3277Test.php
index 36804f459..3ce7e7edf 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3277Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3277Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3435Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3435Test.php
index 9d997dee3..096272401 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3435Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3435Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3464Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3464Test.php
index 90a34f3d5..f466dc725 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3464Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3464Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3495Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3495Test.php
index b85d27e11..5c0b71fac 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3495Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3495Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3534Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3534Test.php
index 72782ec25..3a0146e74 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3534Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3534Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3552Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3552Test.php
index ee83d33be..de3e738cc 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3552Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3552Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3553Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3553Test.php
index 4ae95b46e..73c19f7e7 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3553Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3553Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3613Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3613Test.php
index 71899039e..fc2586643 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3613Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3613Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3665Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3665Test.php
index ba1778698..f4990bc67 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3665Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3665Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3679ImgTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3679ImgTest.php
index 2b9559073..5c9b38074 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3679ImgTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Issue3679ImgTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamedRangeTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamedRangeTest.php
index e4090d983..380c6c2b8 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamedRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamedRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceIssue2109bTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceIssue2109bTest.php
index b970f0844..6c0e6b1e3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceIssue2109bTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceIssue2109bTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceNonStdTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceNonStdTest.php
index cc2c03dce..884454177 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceNonStdTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceNonStdTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceOpenpyxl35Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceOpenpyxl35Test.php
index afb36862a..d582530c6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceOpenpyxl35Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceOpenpyxl35Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespacePurlTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespacePurlTest.php
index e8e9eaba3..7d7ff3fe3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespacePurlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespacePurlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceStdTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceStdTest.php
index 5f8c8bc38..e859cc6a6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceStdTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/NamespaceStdTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/OctothorpeTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/OctothorpeTest.php
index a5c6f2087..1fe65fb87 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/OctothorpeTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/OctothorpeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/OddColumnReadFilter.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/OddColumnReadFilter.php
index 5586d18f7..f1e0c3279 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/OddColumnReadFilter.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/OddColumnReadFilter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetup2Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetup2Test.php
index 12675b418..7f31c7d3b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetup2Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetup2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetupTest.php
index 99a275e43..763dcfb07 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/PageSetupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/PropertiesTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/PropertiesTest.php
index bb414da56..9773a89fd 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/PropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/PropertiesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use DateTimeZone;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/RgbTintTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/RgbTintTest.php
index 96e2003bc..5d2713b79 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/RgbTintTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/RgbTintTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/RibbonTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/RibbonTest.php
index 68b3bb014..6a47b27d5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/RibbonTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/RibbonTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/RichTextTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/RichTextTest.php
index 8fb8baca6..58a7ae136 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/RichTextTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/RichTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/RowBreakTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/RowBreakTest.php
index 9bb75f635..c98e1f528 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/RowBreakTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/RowBreakTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/SharedFormulaTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/SharedFormulaTest.php
index 94f8e3492..b7e453216 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/SharedFormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/SharedFormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetProtectionTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetProtectionTest.php
index 4f81521f7..123b39eb3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetProtectionTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetProtectionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetsXlsxChartTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetsXlsxChartTest.php
index d47ce3114..8af7f6854 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetsXlsxChartTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/SheetsXlsxChartTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Chart\DataSeries;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/SplitsTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/SplitsTest.php
index 424353a7a..ddea4ae0c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/SplitsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/SplitsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/TableTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/TableTest.php
index 43f2e24c7..a9a9b4e1c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/TableTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/TableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/URLImageTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/URLImageTest.php
index e7f990101..46698b2d6 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/URLImageTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/URLImageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/VerticalAlignTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/VerticalAlignTest.php
index 0d3c04676..2829a2dcf 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/VerticalAlignTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/VerticalAlignTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/WorksheetInfoNamesTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/WorksheetInfoNamesTest.php
index 31f971a45..4c56339fb 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/WorksheetInfoNamesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/WorksheetInfoNamesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/Xlsx2Test.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/Xlsx2Test.php
index 4f613f9f8..9a9e1e26d 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/Xlsx2Test.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/Xlsx2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxRootZipFilesTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxRootZipFilesTest.php
index 110c70b01..1142c0c80 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxRootZipFilesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxRootZipFilesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxTest.php
index 8c4efd6d3..ab5081ccc 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/XlsxTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/DataValidationsTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/DataValidationsTest.php
index a90fc63e1..151fc4235 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/DataValidationsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/DataValidationsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/PageSetupTest.php
index 26bb223c0..b5d8a33d5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/PageSetupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/SplitsTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/SplitsTest.php
index 0fd49ca91..7f6b7f6fa 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/SplitsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/SplitsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlActiveSheetTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlActiveSheetTest.php
index 5df4feaa7..740efefe4 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlActiveSheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlActiveSheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlColSpanTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlColSpanTest.php
index a78107fe8..05bd8f5be 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlColSpanTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlColSpanTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlColumnRowHiddenTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlColumnRowHiddenTest.php
index b02f857e8..a17d27fb7 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlColumnRowHiddenTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlColumnRowHiddenTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFilter.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFilter.php
index d41aa00a7..312550505 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFilter.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFilter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\IReadFilter;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFontBoldItalicTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFontBoldItalicTest.php
index 1465c9924..1328a4e08 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFontBoldItalicTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFontBoldItalicTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFreezePanesTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFreezePanesTest.php
index 440bbf50f..b5645b7d3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlFreezePanesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlFreezePanesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlInfoTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlInfoTest.php
index 9bab18779..623fc8be9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlInfoTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlInfoTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlLoadTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlLoadTest.php
index 9846b8617..be159c735 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlLoadTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlLoadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use DateTimeZone;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlOddTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlOddTest.php
index ace299c2c..d479449cf 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlOddTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlOddTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlPropertiesTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlPropertiesTest.php
index 8b4a225d3..bcc23813e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlPropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlPropertiesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlProtectionTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlProtectionTest.php
index acabb90fe..98f77eecf 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlProtectionTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlProtectionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlStyleCoverageTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlStyleCoverageTest.php
index 7fd3f8e2e..fa58c59b3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlStyleCoverageTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlStyleCoverageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlStylesTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlStylesTest.php
index df8f1418c..837526325 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlStylesTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlStylesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
index e2e1a9ce0..33dba1328 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTopLeftTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTopLeftTest.php
index 8320e83ec..30cebca9e 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTopLeftTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTopLeftTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xml;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xml;
diff --git a/tests/PhpSpreadsheetTests/RefRangeTest.php b/tests/PhpSpreadsheetTests/RefRangeTest.php
index c248b40b4..17b4e3cd6 100644
--- a/tests/PhpSpreadsheetTests/RefRangeTest.php
+++ b/tests/PhpSpreadsheetTests/RefRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/ReferenceHelper2Test.php b/tests/PhpSpreadsheetTests/ReferenceHelper2Test.php
index 076ed1b6f..c3f8484f0 100644
--- a/tests/PhpSpreadsheetTests/ReferenceHelper2Test.php
+++ b/tests/PhpSpreadsheetTests/ReferenceHelper2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/ReferenceHelper3Test.php b/tests/PhpSpreadsheetTests/ReferenceHelper3Test.php
index b1ee653fb..4a437a010 100644
--- a/tests/PhpSpreadsheetTests/ReferenceHelper3Test.php
+++ b/tests/PhpSpreadsheetTests/ReferenceHelper3Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/ReferenceHelperTest.php b/tests/PhpSpreadsheetTests/ReferenceHelperTest.php
index b70533f7f..90072d9b1 100644
--- a/tests/PhpSpreadsheetTests/ReferenceHelperTest.php
+++ b/tests/PhpSpreadsheetTests/ReferenceHelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/RichTextTest.php b/tests/PhpSpreadsheetTests/RichTextTest.php
index 04a1d72a9..3ebd099c0 100644
--- a/tests/PhpSpreadsheetTests/RichTextTest.php
+++ b/tests/PhpSpreadsheetTests/RichTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
diff --git a/tests/PhpSpreadsheetTests/SettingsTest.php b/tests/PhpSpreadsheetTests/SettingsTest.php
index 146ddfe13..92668c96e 100644
--- a/tests/PhpSpreadsheetTests/SettingsTest.php
+++ b/tests/PhpSpreadsheetTests/SettingsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpException;
diff --git a/tests/PhpSpreadsheetTests/Shared/CodePageTest.php b/tests/PhpSpreadsheetTests/Shared/CodePageTest.php
index 050cfe0cc..ab3825eea 100644
--- a/tests/PhpSpreadsheetTests/Shared/CodePageTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/CodePageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Shared/Date2Test.php b/tests/PhpSpreadsheetTests/Shared/Date2Test.php
index f1090e3a0..dd9c8a5ab 100644
--- a/tests/PhpSpreadsheetTests/Shared/Date2Test.php
+++ b/tests/PhpSpreadsheetTests/Shared/Date2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalculationException;
diff --git a/tests/PhpSpreadsheetTests/Shared/DateTest.php b/tests/PhpSpreadsheetTests/Shared/DateTest.php
index 95e12b650..116e8981c 100644
--- a/tests/PhpSpreadsheetTests/Shared/DateTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/DateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use DateTimeZone;
diff --git a/tests/PhpSpreadsheetTests/Shared/DgContainerTest.php b/tests/PhpSpreadsheetTests/Shared/DgContainerTest.php
index 0a539f284..57273bf66 100644
--- a/tests/PhpSpreadsheetTests/Shared/DgContainerTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/DgContainerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Shared/DrawingTest.php b/tests/PhpSpreadsheetTests/Shared/DrawingTest.php
index 22cd1dbbc..972576e60 100644
--- a/tests/PhpSpreadsheetTests/Shared/DrawingTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/DrawingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\Drawing;
diff --git a/tests/PhpSpreadsheetTests/Shared/ExactFontTest.php b/tests/PhpSpreadsheetTests/Shared/ExactFontTest.php
index b8573d3bf..3beef8778 100644
--- a/tests/PhpSpreadsheetTests/Shared/ExactFontTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/ExactFontTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
diff --git a/tests/PhpSpreadsheetTests/Shared/FileTest.php b/tests/PhpSpreadsheetTests/Shared/FileTest.php
index cd040364a..f96f56ead 100644
--- a/tests/PhpSpreadsheetTests/Shared/FileTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/FileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Shared/Font2Test.php b/tests/PhpSpreadsheetTests/Shared/Font2Test.php
index adff9eba6..2bfa429ef 100644
--- a/tests/PhpSpreadsheetTests/Shared/Font2Test.php
+++ b/tests/PhpSpreadsheetTests/Shared/Font2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\Font;
diff --git a/tests/PhpSpreadsheetTests/Shared/Font3Test.php b/tests/PhpSpreadsheetTests/Shared/Font3Test.php
index e91e7acf0..029712390 100644
--- a/tests/PhpSpreadsheetTests/Shared/Font3Test.php
+++ b/tests/PhpSpreadsheetTests/Shared/Font3Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception as SSException;
diff --git a/tests/PhpSpreadsheetTests/Shared/FontFileNameTest.php b/tests/PhpSpreadsheetTests/Shared/FontFileNameTest.php
index 460a7851d..06ee3243b 100644
--- a/tests/PhpSpreadsheetTests/Shared/FontFileNameTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/FontFileNameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception as SSException;
diff --git a/tests/PhpSpreadsheetTests/Shared/FontTest.php b/tests/PhpSpreadsheetTests/Shared/FontTest.php
index 699041ee1..27ebe4398 100644
--- a/tests/PhpSpreadsheetTests/Shared/FontTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/FontTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\Font;
diff --git a/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php b/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php
index 2bf88b3ff..6e80a42e0 100644
--- a/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php
+++ b/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\OLE;
diff --git a/tests/PhpSpreadsheetTests/Shared/OLEReadTest.php b/tests/PhpSpreadsheetTests/Shared/OLEReadTest.php
index 7fe485c9c..079014665 100644
--- a/tests/PhpSpreadsheetTests/Shared/OLEReadTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/OLEReadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\OLERead;
diff --git a/tests/PhpSpreadsheetTests/Shared/OLETest.php b/tests/PhpSpreadsheetTests/Shared/OLETest.php
index db81272c5..f4fe368d4 100644
--- a/tests/PhpSpreadsheetTests/Shared/OLETest.php
+++ b/tests/PhpSpreadsheetTests/Shared/OLETest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Reader\Exception as ReaderException;
diff --git a/tests/PhpSpreadsheetTests/Shared/PasswordHasherTest.php b/tests/PhpSpreadsheetTests/Shared/PasswordHasherTest.php
index 97e63deab..78a89386c 100644
--- a/tests/PhpSpreadsheetTests/Shared/PasswordHasherTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/PasswordHasherTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpException;
diff --git a/tests/PhpSpreadsheetTests/Shared/PasswordReloadTest.php b/tests/PhpSpreadsheetTests/Shared/PasswordReloadTest.php
index 14007416e..50b5b1f93 100644
--- a/tests/PhpSpreadsheetTests/Shared/PasswordReloadTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/PasswordReloadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\PasswordHasher;
diff --git a/tests/PhpSpreadsheetTests/Shared/StringHelperInvalidCharTest.php b/tests/PhpSpreadsheetTests/Shared/StringHelperInvalidCharTest.php
index 546794999..5ee095377 100644
--- a/tests/PhpSpreadsheetTests/Shared/StringHelperInvalidCharTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/StringHelperInvalidCharTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
diff --git a/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php b/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
index bcbcd5d21..b5634b80b 100644
--- a/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
diff --git a/tests/PhpSpreadsheetTests/Shared/TimeZoneTest.php b/tests/PhpSpreadsheetTests/Shared/TimeZoneTest.php
index 3db13b25c..05224fe07 100644
--- a/tests/PhpSpreadsheetTests/Shared/TimeZoneTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/TimeZoneTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
index 82c97efa4..ec44ff4c0 100644
--- a/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/ExponentialBestFitTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
 
 use PhpOffice\PhpSpreadsheet\Shared\Trend\ExponentialBestFit;
diff --git a/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
index 0dafa66f7..6f150ffa9 100644
--- a/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/Trend/LinearBestFitTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared\Trend;
 
 use PhpOffice\PhpSpreadsheet\Shared\Trend\LinearBestFit;
diff --git a/tests/PhpSpreadsheetTests/Shared/XmlWriterTest.php b/tests/PhpSpreadsheetTests/Shared/XmlWriterTest.php
index 200325137..47f66d102 100644
--- a/tests/PhpSpreadsheetTests/Shared/XmlWriterTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/XmlWriterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Shared;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/SpreadsheetCoverageTest.php b/tests/PhpSpreadsheetTests/SpreadsheetCoverageTest.php
index 54febf7b9..196dabd33 100644
--- a/tests/PhpSpreadsheetTests/SpreadsheetCoverageTest.php
+++ b/tests/PhpSpreadsheetTests/SpreadsheetCoverageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Exception as SSException;
diff --git a/tests/PhpSpreadsheetTests/SpreadsheetTest.php b/tests/PhpSpreadsheetTests/SpreadsheetTest.php
index 5c61eaf2e..fe4e98643 100644
--- a/tests/PhpSpreadsheetTests/SpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/SpreadsheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/AlignmentMiddleTest.php b/tests/PhpSpreadsheetTests/Style/AlignmentMiddleTest.php
index 1d260a6e5..2fcb71918 100644
--- a/tests/PhpSpreadsheetTests/Style/AlignmentMiddleTest.php
+++ b/tests/PhpSpreadsheetTests/Style/AlignmentMiddleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Style/AlignmentTest.php b/tests/PhpSpreadsheetTests/Style/AlignmentTest.php
index 6f50ce225..0f0ba5e15 100644
--- a/tests/PhpSpreadsheetTests/Style/AlignmentTest.php
+++ b/tests/PhpSpreadsheetTests/Style/AlignmentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Style/BorderRangeTest.php b/tests/PhpSpreadsheetTests/Style/BorderRangeTest.php
index aec5520d9..926dcb22e 100644
--- a/tests/PhpSpreadsheetTests/Style/BorderRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Style/BorderRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Style/BorderTest.php b/tests/PhpSpreadsheetTests/Style/BorderTest.php
index cf6cd3a96..9f18f0766 100644
--- a/tests/PhpSpreadsheetTests/Style/BorderTest.php
+++ b/tests/PhpSpreadsheetTests/Style/BorderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Style/ColorIndexTest.php b/tests/PhpSpreadsheetTests/Style/ColorIndexTest.php
index 2913f3f5b..31d980ebd 100644
--- a/tests/PhpSpreadsheetTests/Style/ColorIndexTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ColorIndexTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx\Styles;
diff --git a/tests/PhpSpreadsheetTests/Style/ColorTest.php b/tests/PhpSpreadsheetTests/Style/ColorTest.php
index e8c41ab9b..4848f5cf9 100644
--- a/tests/PhpSpreadsheetTests/Style/ColorTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ColorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Style\Color;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalBoolTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalBoolTest.php
index 2e50fcedb..e4b0c7fcf 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalBoolTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalBoolTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/CellMatcherTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/CellMatcherTest.php
index 84e5dcd29..505991d4e 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/CellMatcherTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/CellMatcherTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/BlankWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/BlankWizardTest.php
index 025376d9b..027c0674e 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/BlankWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/BlankWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/CellValueWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/CellValueWizardTest.php
index 04974061c..7ccc860fc 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/CellValueWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/CellValueWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DateValueWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DateValueWizardTest.php
index 175dc03c2..824066cb9 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DateValueWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DateValueWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DuplicatesWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DuplicatesWizardTest.php
index c6ed6e034..2b280a7aa 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DuplicatesWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/DuplicatesWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ErrorWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ErrorWizardTest.php
index f58b90e45..b845318fe 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ErrorWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ErrorWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ExpressionWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ExpressionWizardTest.php
index 6b6547eb8..7ce0c2be0 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ExpressionWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/ExpressionWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/TextValueWizardTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/TextValueWizardTest.php
index 505e3d7c7..de6d22aaf 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/TextValueWizardTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/TextValueWizardTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/WizardFactoryTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/WizardFactoryTest.php
index 06b900c07..b3ddc9b66 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/WizardFactoryTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalFormatting/Wizard/WizardFactoryTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\ConditionalFormatting\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Style/ConditionalTest.php b/tests/PhpSpreadsheetTests/Style/ConditionalTest.php
index 064a52f18..e29043166 100644
--- a/tests/PhpSpreadsheetTests/Style/ConditionalTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ConditionalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Style\Conditional;
diff --git a/tests/PhpSpreadsheetTests/Style/ExportArrayTest.php b/tests/PhpSpreadsheetTests/Style/ExportArrayTest.php
index a062b4cf6..5709d5c0a 100644
--- a/tests/PhpSpreadsheetTests/Style/ExportArrayTest.php
+++ b/tests/PhpSpreadsheetTests/Style/ExportArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Style/FillTest.php b/tests/PhpSpreadsheetTests/Style/FillTest.php
index 18ee224dc..f55b68110 100644
--- a/tests/PhpSpreadsheetTests/Style/FillTest.php
+++ b/tests/PhpSpreadsheetTests/Style/FillTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Style\Color;
diff --git a/tests/PhpSpreadsheetTests/Style/FontTest.php b/tests/PhpSpreadsheetTests/Style/FontTest.php
index 6cd4d950c..20df75b1a 100644
--- a/tests/PhpSpreadsheetTests/Style/FontTest.php
+++ b/tests/PhpSpreadsheetTests/Style/FontTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/AccountingTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/AccountingTest.php
index 269ecdcdc..a71153bd4 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/AccountingTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/AccountingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use NumberFormatter;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/CurrencyTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/CurrencyTest.php
index a84d5566d..dd37d2fe3 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/CurrencyTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/CurrencyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use NumberFormatter;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTest.php
index a8b7a4ff1..cc19a4129 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat\Wizard\Date;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTimeTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTimeTest.php
index 7a1cc084b..17fedffa3 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTimeTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DateTimeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat\Wizard\Date;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DurationTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DurationTest.php
index c7876beb9..0804deee0 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DurationTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/DurationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat\Wizard\Duration;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/NumberTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/NumberTest.php
index 9f9a51a59..950496ed4 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/NumberTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/NumberTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use NumberFormatter;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/PercentageTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/PercentageTest.php
index 913801b89..23f45b9c9 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/PercentageTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/PercentageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use NumberFormatter;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/ScientificTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/ScientificTest.php
index 5f1704695..9120284c6 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/ScientificTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/ScientificTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use NumberFormatter;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/TimeTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/TimeTest.php
index 02249de33..de86ffe96 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/TimeTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormat/Wizard/TimeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style\NumberFormat\Wizard;
 
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat\Wizard\Time;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormatBuiltinTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormatBuiltinTest.php
index dd3d672ae..5e33ff314 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormatBuiltinTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormatBuiltinTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormatRoundTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormatRoundTest.php
index 3401b0201..646c7f4f0 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormatRoundTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormatRoundTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
index ed28aed8f..47d473088 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
diff --git a/tests/PhpSpreadsheetTests/Style/StyleTest.php b/tests/PhpSpreadsheetTests/Style/StyleTest.php
index 13998546a..be67a5e79 100644
--- a/tests/PhpSpreadsheetTests/Style/StyleTest.php
+++ b/tests/PhpSpreadsheetTests/Style/StyleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Style;
 
 use PhpOffice\PhpSpreadsheet\Cell\CellAddress;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterAverageTop10Test.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterAverageTop10Test.php
index 1e8274690..55c80dfc6 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterAverageTop10Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterAverageTop10Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\AutoFilter\Column;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomNumericTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomNumericTest.php
index 72a3d1a6b..e36135a6c 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomNumericTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomNumericTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomTextTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomTextTest.php
index a40797b77..dcaba9ef3 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomTextTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterCustomTextTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\AutoFilter\Column;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterMonthTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterMonthTest.php
index 480803d8e..742e6cbc3 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterMonthTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterMonthTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterQuarterTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterQuarterTest.php
index 9fd1a5b0d..20fd146b2 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterQuarterTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterQuarterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTest.php
index ebec36864..7b1583d54 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTodayTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTodayTest.php
index 588316ed2..dfe8b5740 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTodayTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterTodayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterWeekTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterWeekTest.php
index 8b1d41236..cbd5379e9 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterWeekTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterWeekTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterYearTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterYearTest.php
index 4baa8dc05..84316d2d5 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterYearTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/AutoFilterYearTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use DateTimeImmutable;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
index c94cb3a4b..4e7e48348 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DateGroupTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DateGroupTest.php
index a89ebd5b5..dc02ca7b8 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DateGroupTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DateGroupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\AutoFilter\Column;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DeleteAutoFilterTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DeleteAutoFilterTest.php
index f1ef1aca3..6fd7019dc 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DeleteAutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/DeleteAutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 class DeleteAutoFilterTest extends SetupTeardown
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleCustomTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleCustomTest.php
index bffd885e4..7f643e8ed 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleCustomTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleCustomTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\AutoFilter\Column;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleDateGroupTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleDateGroupTest.php
index 3a32a9ebf..d09ce649e 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleDateGroupTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleDateGroupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleTest.php
index c9eaa4f2e..0ab5ca234 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/RuleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/SetupTeardown.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/SetupTeardown.php
index c77cf7f88..925c97c46 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/SetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/SetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\AutoFilter;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoSizeTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoSizeTest.php
index e774b04cc..4a4f488bb 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoSizeTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoSizeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowTest.php b/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowTest.php
index 48a04685b..14ef832e5 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowUndeprecatedTest.php b/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowUndeprecatedTest.php
index 630cf1db1..40f1d03e2 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowUndeprecatedTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ByColumnAndRowUndeprecatedTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIterator2Test.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIterator2Test.php
index 88f1e7d7c..894a8adf7 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIterator2Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIterator2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIteratorTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIteratorTest.php
index 02b964265..593d7f149 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIteratorTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnCellIteratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnDimension2Test.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnDimension2Test.php
index f5878eef5..e65c003e8 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnDimension2Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnDimension2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Helper\Dimension;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnDimensionTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnDimensionTest.php
index 1994fa81a..ee5cc92ed 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnDimensionTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnDimensionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Helper\Dimension;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
index 47c403729..b1e0f07a7 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorTest.php
index 7bb20cd62..8182992ee 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as Except;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnTest.php
index 0e265156f..b2c0b7515 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ConditionalStyleTest.php b/tests/PhpSpreadsheetTests/Worksheet/ConditionalStyleTest.php
index 6221fee4b..e88474039 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ConditionalStyleTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ConditionalStyleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/DefaultPaperSizeTest.php b/tests/PhpSpreadsheetTests/Worksheet/DefaultPaperSizeTest.php
index 5ab3c2825..6aecd2a78 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/DefaultPaperSizeTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/DefaultPaperSizeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/DrawingTest.php b/tests/PhpSpreadsheetTests/Worksheet/DrawingTest.php
index 17e17e192..4ab1ca2e2 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/DrawingTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/DrawingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/IteratorTest.php b/tests/PhpSpreadsheetTests/Worksheet/IteratorTest.php
index b2a063439..cf3eca54e 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/IteratorTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/IteratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/MemoryDrawingTest.php b/tests/PhpSpreadsheetTests/Worksheet/MemoryDrawingTest.php
index dd992dae1..307496143 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/MemoryDrawingTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/MemoryDrawingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use GdImage;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php b/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
index ab79ad830..7f0b04df6 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/PageBreakTest.php b/tests/PhpSpreadsheetTests/Worksheet/PageBreakTest.php
index cbeb96d68..a211e2ad7 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/PageBreakTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/PageBreakTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\CellAddress;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/PageMarginsTest.php b/tests/PhpSpreadsheetTests/Worksheet/PageMarginsTest.php
index 084e6f786..f6795fc99 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/PageMarginsTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/PageMarginsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\PageMargins;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ProtectionTest.php b/tests/PhpSpreadsheetTests/Worksheet/ProtectionTest.php
index 0be172b0e..8f1e2733d 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ProtectionTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ProtectionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Protection;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RemoveTest.php b/tests/PhpSpreadsheetTests/Worksheet/RemoveTest.php
index 73c04c071..0dcab2d10 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RemoveTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RemoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowCellIterator2Test.php b/tests/PhpSpreadsheetTests/Worksheet/RowCellIterator2Test.php
index 4b5f624e8..1f3e883e2 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowCellIterator2Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowCellIterator2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowCellIteratorTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowCellIteratorTest.php
index 9afda3cb9..09578ffb7 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowCellIteratorTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowCellIteratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowDimensionSaveTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowDimensionSaveTest.php
index ab09de26e..8bce18793 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowDimensionSaveTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowDimensionSaveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowDimensionTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowDimensionTest.php
index a5b5a04d0..1782ba52f 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowDimensionTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowDimensionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Helper\Dimension;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
index ec062a032..1d8a83caf 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorTest.php
index 3ba3654e4..2ddc9fb6c 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as Except;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowTest.php
index dd0eb78fc..810e763d4 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/SheetViewTest.php b/tests/PhpSpreadsheetTests/Worksheet/SheetViewTest.php
index f37c79581..38926181f 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/SheetViewTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/SheetViewTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/ColumnTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/ColumnTest.php
index c7edd86a0..be184af1b 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/ColumnTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/ColumnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/FormulaTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/FormulaTest.php
index 25dc27025..4faba0bee 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/FormulaTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/FormulaTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3635Test.php b/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3635Test.php
index d004d8d8b..ed687e14d 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3635Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3635Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Table;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3659Test.php b/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3659Test.php
index fcb4c6487..3ec7c6bd5 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3659Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/Issue3659Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Table;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/RemoveTableTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/RemoveTableTest.php
index fb2bb9397..be46b663d 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/RemoveTableTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/RemoveTableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Table;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/SetupTeardown.php b/tests/PhpSpreadsheetTests/Worksheet/Table/SetupTeardown.php
index 76e914f7d..41bf86ed2 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/SetupTeardown.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/SetupTeardown.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/TableStyleTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/TableStyleTest.php
index 830cc87b8..a84da3814 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/TableStyleTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/TableStyleTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Table;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
index 17f9bfd6c..33acde125 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet\Table;
 
 use PhpOffice\PhpSpreadsheet\Cell\AddressRange;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Worksheet2Test.php b/tests/PhpSpreadsheetTests/Worksheet/Worksheet2Test.php
index 2b1a2b5d8..8735caccd 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Worksheet2Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Worksheet2Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Worksheet3Test.php b/tests/PhpSpreadsheetTests/Worksheet/Worksheet3Test.php
index 04320cb83..addd0f2ef 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Worksheet3Test.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Worksheet3Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/WorksheetNamedRangesTest.php b/tests/PhpSpreadsheetTests/Worksheet/WorksheetNamedRangesTest.php
index 3b7f64c57..67777ad6c 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/WorksheetNamedRangesTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/WorksheetNamedRangesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/WorksheetParentTest.php b/tests/PhpSpreadsheetTests/Worksheet/WorksheetParentTest.php
index 2a6634067..b5960ea30 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/WorksheetParentTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/WorksheetParentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use PhpOffice\PhpSpreadsheet\Exception as SpException;
diff --git a/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php b/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
index c30113436..87e7eab61 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/WorksheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
 
 use Exception;
@@ -607,7 +609,7 @@ class WorksheetTest extends TestCase
 
         $cellRange = new CellRange(new CellAddress($fromCell), new CellAddress($toCell));
 
-        self::assertSame($expected, $worksheet->rangeToArray($cellRange));
+        self::assertSame($expected, $worksheet->rangeToArray((string) $cellRange));
     }
 
     public static function rangeToArrayProvider(): array
diff --git a/tests/PhpSpreadsheetTests/Writer/Csv/CsvEnclosureTest.php b/tests/PhpSpreadsheetTests/Writer/Csv/CsvEnclosureTest.php
index 383f83aba..ffbdf453c 100644
--- a/tests/PhpSpreadsheetTests/Writer/Csv/CsvEnclosureTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Csv/CsvEnclosureTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv as CsvReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php b/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php
index 9b7d16aae..7330ae869 100644
--- a/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv as CsvReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Csv/CsvOutputEncodingTest.php b/tests/PhpSpreadsheetTests/Writer/Csv/CsvOutputEncodingTest.php
index 81e4428e2..41562a585 100644
--- a/tests/PhpSpreadsheetTests/Writer/Csv/CsvOutputEncodingTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Csv/CsvOutputEncodingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Csv;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Csv/CsvWriteTest.php b/tests/PhpSpreadsheetTests/Writer/Csv/CsvWriteTest.php
index aa9a8fc37..a45b2da7f 100644
--- a/tests/PhpSpreadsheetTests/Writer/Csv/CsvWriteTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Csv/CsvWriteTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Csv;
 
 use PhpOffice\PhpSpreadsheet\Reader\Csv as CsvReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Dompdf/PaperSizeArrayTest.php b/tests/PhpSpreadsheetTests/Writer/Dompdf/PaperSizeArrayTest.php
index 815d7e3dc..adf2aa19a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Dompdf/PaperSizeArrayTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Dompdf/PaperSizeArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Dompdf;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Dompdf/TextRotationTest.php b/tests/PhpSpreadsheetTests/Writer/Dompdf/TextRotationTest.php
index 2aa9d5ed8..7e8ee3088 100644
--- a/tests/PhpSpreadsheetTests/Writer/Dompdf/TextRotationTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Dompdf/TextRotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Dompdf;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/AllOrOneSheetTest.php b/tests/PhpSpreadsheetTests/Writer/Html/AllOrOneSheetTest.php
index 31ed438e2..2a0cb9feb 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/AllOrOneSheetTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/AllOrOneSheetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php b/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
index 818ee9a32..2684cd559 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/CallbackTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/ExtendForChartsAndImagesTest.php b/tests/PhpSpreadsheetTests/Writer/Html/ExtendForChartsAndImagesTest.php
index e3d23230c..380219659 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/ExtendForChartsAndImagesTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/ExtendForChartsAndImagesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/FixHeightTest.php b/tests/PhpSpreadsheetTests/Writer/Html/FixHeightTest.php
index 745aabb69..48b9ba7d5 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/FixHeightTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/FixHeightTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/GridlinesTest.php b/tests/PhpSpreadsheetTests/Writer/Html/GridlinesTest.php
index 08af7c59f..89455bd03 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/GridlinesTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/GridlinesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/HtmlCommentsTest.php b/tests/PhpSpreadsheetTests/Writer/Html/HtmlCommentsTest.php
index 00fae1ade..53c62ece0 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/HtmlCommentsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/HtmlCommentsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php b/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
index fc4d30269..7bf5e121c 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/ImageCopyTest.php b/tests/PhpSpreadsheetTests/Writer/Html/ImageCopyTest.php
index adee76b08..83e8bdf04 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/ImageCopyTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/ImageCopyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls as XlsReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/ImagesRootTest.php b/tests/PhpSpreadsheetTests/Writer/Html/ImagesRootTest.php
index b36a87c0b..395287575 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/ImagesRootTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/ImagesRootTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/InvalidFileNameTest.php b/tests/PhpSpreadsheetTests/Writer/Html/InvalidFileNameTest.php
index 36a40e965..e4621c58a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/InvalidFileNameTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/InvalidFileNameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/Issue3678Test.php b/tests/PhpSpreadsheetTests/Writer/Html/Issue3678Test.php
index 5c0a7cd02..cabcaca8f 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/Issue3678Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/Issue3678Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/MemoryDrawingOffsetTest.php b/tests/PhpSpreadsheetTests/Writer/Html/MemoryDrawingOffsetTest.php
index e367f174d..ab2baea81 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/MemoryDrawingOffsetTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/MemoryDrawingOffsetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/RepeatedRowsTest.php b/tests/PhpSpreadsheetTests/Writer/Html/RepeatedRowsTest.php
index 2a0f60c1a..50d505d9a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/RepeatedRowsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/RepeatedRowsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use DOMDocument;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/TextRotationTest.php b/tests/PhpSpreadsheetTests/Writer/Html/TextRotationTest.php
index da9284576..2480e04b9 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/TextRotationTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/TextRotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/VisibilityTest.php b/tests/PhpSpreadsheetTests/Writer/Html/VisibilityTest.php
index 1c1ffb069..75987f83a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/VisibilityTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/VisibilityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/XssVulnerabilityTest.php b/tests/PhpSpreadsheetTests/Writer/Html/XssVulnerabilityTest.php
index 25933179b..9f7d6894d 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/XssVulnerabilityTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/XssVulnerabilityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Html;
 
 use PhpOffice\PhpSpreadsheet\IOFactory;
diff --git a/tests/PhpSpreadsheetTests/Writer/Mpdf/ImageCopyPdfTest.php b/tests/PhpSpreadsheetTests/Writer/Mpdf/ImageCopyPdfTest.php
index 5d31bc010..c9aae25b7 100644
--- a/tests/PhpSpreadsheetTests/Writer/Mpdf/ImageCopyPdfTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Mpdf/ImageCopyPdfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Mpdf;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls as XlsReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Mpdf/OrientationTest.php b/tests/PhpSpreadsheetTests/Writer/Mpdf/OrientationTest.php
index c04e8432e..8f5fde5bc 100644
--- a/tests/PhpSpreadsheetTests/Writer/Mpdf/OrientationTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Mpdf/OrientationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Mpdf;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Mpdf/TextRotationTest.php b/tests/PhpSpreadsheetTests/Writer/Mpdf/TextRotationTest.php
index 000a33b4b..4f9c7557c 100644
--- a/tests/PhpSpreadsheetTests/Writer/Mpdf/TextRotationTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Mpdf/TextRotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Mpdf;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/AutoFilterTest.php
index 4368ef76e..ddfe85570 100644
--- a/tests/PhpSpreadsheetTests/Writer/Ods/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/AutoFilterTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Ods;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
index 81c244a76..c2769da25 100644
--- a/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Ods;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/DefinedNamesTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/DefinedNamesTest.php
index 1b2e30b28..771b90b6e 100644
--- a/tests/PhpSpreadsheetTests/Writer/Ods/DefinedNamesTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/DefinedNamesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Ods;
 
 use PhpOffice\PhpSpreadsheet\NamedFormula;
diff --git a/tests/PhpSpreadsheetTests/Writer/Ods/MergeRangeTest.php b/tests/PhpSpreadsheetTests/Writer/Ods/MergeRangeTest.php
index 30ca69700..c029b08d0 100644
--- a/tests/PhpSpreadsheetTests/Writer/Ods/MergeRangeTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Ods/MergeRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Ods;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/PreCalcTest.php b/tests/PhpSpreadsheetTests/Writer/PreCalcTest.php
index 04cbc77f8..8dd6ee4a3 100644
--- a/tests/PhpSpreadsheetTests/Writer/PreCalcTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/PreCalcTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Writer/RetainSelectedCellsTest.php b/tests/PhpSpreadsheetTests/Writer/RetainSelectedCellsTest.php
index 13670b858..70e2ccd2b 100644
--- a/tests/PhpSpreadsheetTests/Writer/RetainSelectedCellsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/RetainSelectedCellsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/BooleanLiteralTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/BooleanLiteralTest.php
index 3528308b1..69d267f4e 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/BooleanLiteralTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/BooleanLiteralTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/FormulaErrTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/FormulaErrTest.php
index 48cba12a6..b449a1068 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/FormulaErrTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/FormulaErrTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\NamedRange;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/Issue642Test.php b/tests/PhpSpreadsheetTests/Writer/Xls/Issue642Test.php
index 1a86c7993..133424984 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/Issue642Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/Issue642Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/ParserTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/ParserTest.php
index 38fd29d33..9a283ddbe 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/ParserTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/ParserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/Sample19Test.php b/tests/PhpSpreadsheetTests/Writer/Xls/Sample19Test.php
index 13fa9fa1d..23d3bc113 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/Sample19Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/Sample19Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/VisibilityTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/VisibilityTest.php
index 07aeaeaa5..cd0de111d 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/VisibilityTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/VisibilityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
index a93662fd9..532f22b0b 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/XlsGifBmpTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/XlsGifBmpTest.php
index 412ca45be..5f9c5d91d 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/XlsGifBmpTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/XlsGifBmpTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
 
 use DateTime;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ArrayFormulaPrefixTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ArrayFormulaPrefixTest.php
index 1e9505af5..e6d6e085f 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/ArrayFormulaPrefixTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ArrayFormulaPrefixTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/CalculationErrorTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/CalculationErrorTest.php
index d4b4e6eab..9b61bf636 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/CalculationErrorTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/CalculationErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFillTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFillTest.php
index 541a6193b..42930c1db 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFillTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalFillTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalTest.php
index da2e0eeca..bceed1050 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ConditionalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsInsertRowsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsInsertRowsTest.php
index e2cbbff37..fcae0fd05 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsInsertRowsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsInsertRowsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsTest.php
index 26edd23d0..26c55a056 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/DrawingsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Comment;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/FloatsRetainedTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/FloatsRetainedTest.php
index 126022dc8..85b68cc40 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/FloatsRetainedTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/FloatsRetainedTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as Reader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/FunctionPrefixTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/FunctionPrefixTest.php
index 3efeb65c7..85c0c67e6 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/FunctionPrefixTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/FunctionPrefixTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Writer\Xlsx\FunctionPrefix;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2082Test.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2082Test.php
index 1f72a3821..11a3c6f25 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2082Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2082Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2266Test.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2266Test.php
index da6fea4e6..637dec1d0 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2266Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2266Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as Reader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2368Test.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2368Test.php
index 8915f5df9..6a03a9cbb 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2368Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue2368Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue3443Test.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue3443Test.php
index a54cb46ce..8b658bbf0 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue3443Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/Issue3443Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
index 7a4b9ca28..2163e263a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/MemoryDrawingTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/MemoryDrawingTest.php
index c30cb4f09..67380e1ba 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/MemoryDrawingTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/MemoryDrawingTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use GdImage;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/StartsWithHashTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/StartsWithHashTest.php
index ebc3c92f9..9b87c11ad 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/StartsWithHashTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/StartsWithHashTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/TableTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/TableTest.php
index c3de92046..6636af5dd 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/TableTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/TableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeColorsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeColorsTest.php
index 7eae3e517..1b18603c5 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeColorsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeColorsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeFontsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeFontsTest.php
index 8c99ac977..6e7f66f0b 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeFontsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/ThemeFontsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/Unparsed2396Test.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/Unparsed2396Test.php
index 92a05efa6..a27758b38 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/Unparsed2396Test.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/Unparsed2396Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as Reader;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataCloneTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataCloneTest.php
index eba7288f1..94ddaf42e 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataCloneTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataCloneTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Shared\File;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataTest.php
index 72d85a25b..f31e6718c 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/UnparsedDataTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use Exception;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/VisibilityTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/VisibilityTest.php
index 8ff6ceff4..af3b040b1 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/VisibilityTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/VisibilityTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php
index b43b13588..76dde67aa 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 6b6dc01c8..4cd23357d 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -1,9 +1,8 @@
 <?php
 
-setlocale(LC_ALL, 'en_US.utf8');
+declare(strict_types=1);
 
-// PHP 5.3 Compat
-//date_default_timezone_set('Europe/London');
+setlocale(LC_ALL, 'en_US.utf8');
 
 function phpunit10ErrorHandler(int $errno, string $errstr, string $filename, int $lineno): bool
 {
diff --git a/tests/data/Calculation/BinaryComparisonOperations.php b/tests/data/Calculation/BinaryComparisonOperations.php
index 8a6d79f87..bbaba2840 100644
--- a/tests/data/Calculation/BinaryComparisonOperations.php
+++ b/tests/data/Calculation/BinaryComparisonOperations.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [null, null, '=', true, true],
     [null, null, '<>', false, false],
diff --git a/tests/data/Calculation/Calculation.php b/tests/data/Calculation/Calculation.php
index e49bed9fe..27cafc90b 100644
--- a/tests/data/Calculation/Calculation.php
+++ b/tests/data/Calculation/Calculation.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 function calculationTestDataGenerator(): array
 {
     $dataArray1 = [
diff --git a/tests/data/Calculation/DateTime/DATE.php b/tests/data/Calculation/DateTime/DATE.php
index 3bed36f1c..d585846da 100644
--- a/tests/data/Calculation/DateTime/DATE.php
+++ b/tests/data/Calculation/DateTime/DATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/DATEDIF.php b/tests/data/Calculation/DateTime/DATEDIF.php
index 1da3c6643..80746a7e0 100644
--- a/tests/data/Calculation/DateTime/DATEDIF.php
+++ b/tests/data/Calculation/DateTime/DATEDIF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/DATEVALUE.php b/tests/data/Calculation/DateTime/DATEVALUE.php
index 508a06c1e..3f5ea10ec 100644
--- a/tests/data/Calculation/DateTime/DATEVALUE.php
+++ b/tests/data/Calculation/DateTime/DATEVALUE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 //  Date String, Result
diff --git a/tests/data/Calculation/DateTime/DAY.php b/tests/data/Calculation/DateTime/DAY.php
index a2ccc55c3..b23db5094 100644
--- a/tests/data/Calculation/DateTime/DAY.php
+++ b/tests/data/Calculation/DateTime/DAY.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 //  Excel Result, Argument
diff --git a/tests/data/Calculation/DateTime/DAYOpenOffice.php b/tests/data/Calculation/DateTime/DAYOpenOffice.php
index a9cef9e60..9f3799fb1 100644
--- a/tests/data/Calculation/DateTime/DAYOpenOffice.php
+++ b/tests/data/Calculation/DateTime/DAYOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 //  OpenOffice Result, Argument
diff --git a/tests/data/Calculation/DateTime/DAYS.php b/tests/data/Calculation/DateTime/DAYS.php
index 8fd2a91a5..811198c09 100644
--- a/tests/data/Calculation/DateTime/DAYS.php
+++ b/tests/data/Calculation/DateTime/DAYS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/DAYS360.php b/tests/data/Calculation/DateTime/DAYS360.php
index 02ea5f377..aeadaae2c 100644
--- a/tests/data/Calculation/DateTime/DAYS360.php
+++ b/tests/data/Calculation/DateTime/DAYS360.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/EDATE.php b/tests/data/Calculation/DateTime/EDATE.php
index 197f43335..c4d284677 100644
--- a/tests/data/Calculation/DateTime/EDATE.php
+++ b/tests/data/Calculation/DateTime/EDATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/EOMONTH.php b/tests/data/Calculation/DateTime/EOMONTH.php
index 57edf58bc..8143a40df 100644
--- a/tests/data/Calculation/DateTime/EOMONTH.php
+++ b/tests/data/Calculation/DateTime/EOMONTH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/HOUR.php b/tests/data/Calculation/DateTime/HOUR.php
index 0ed74119b..ea4fb3267 100644
--- a/tests/data/Calculation/DateTime/HOUR.php
+++ b/tests/data/Calculation/DateTime/HOUR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/ISOWEEKNUM.php b/tests/data/Calculation/DateTime/ISOWEEKNUM.php
index 0d48ef1c2..6758f0f13 100644
--- a/tests/data/Calculation/DateTime/ISOWEEKNUM.php
+++ b/tests/data/Calculation/DateTime/ISOWEEKNUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/ISOWEEKNUM1904.php b/tests/data/Calculation/DateTime/ISOWEEKNUM1904.php
index 6eedca42b..649c45708 100644
--- a/tests/data/Calculation/DateTime/ISOWEEKNUM1904.php
+++ b/tests/data/Calculation/DateTime/ISOWEEKNUM1904.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/MINUTE.php b/tests/data/Calculation/DateTime/MINUTE.php
index 1ef39982e..cb984be9a 100644
--- a/tests/data/Calculation/DateTime/MINUTE.php
+++ b/tests/data/Calculation/DateTime/MINUTE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/MONTH.php b/tests/data/Calculation/DateTime/MONTH.php
index 631ac791a..4aed030fe 100644
--- a/tests/data/Calculation/DateTime/MONTH.php
+++ b/tests/data/Calculation/DateTime/MONTH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/NETWORKDAYS.php b/tests/data/Calculation/DateTime/NETWORKDAYS.php
index cc4ef578d..f364c5193 100644
--- a/tests/data/Calculation/DateTime/NETWORKDAYS.php
+++ b/tests/data/Calculation/DateTime/NETWORKDAYS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/SECOND.php b/tests/data/Calculation/DateTime/SECOND.php
index 177c471d6..112838520 100644
--- a/tests/data/Calculation/DateTime/SECOND.php
+++ b/tests/data/Calculation/DateTime/SECOND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/TIME.php b/tests/data/Calculation/DateTime/TIME.php
index 36460cdc3..7d46b09fe 100644
--- a/tests/data/Calculation/DateTime/TIME.php
+++ b/tests/data/Calculation/DateTime/TIME.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/TIMEVALUE.php b/tests/data/Calculation/DateTime/TIMEVALUE.php
index 44f4212a9..008d923fc 100644
--- a/tests/data/Calculation/DateTime/TIMEVALUE.php
+++ b/tests/data/Calculation/DateTime/TIMEVALUE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/WEEKDAY.php b/tests/data/Calculation/DateTime/WEEKDAY.php
index 32423f070..bd66b8c8d 100644
--- a/tests/data/Calculation/DateTime/WEEKDAY.php
+++ b/tests/data/Calculation/DateTime/WEEKDAY.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/WEEKNUM.php b/tests/data/Calculation/DateTime/WEEKNUM.php
index c77ff1a57..bb6ee2a2a 100644
--- a/tests/data/Calculation/DateTime/WEEKNUM.php
+++ b/tests/data/Calculation/DateTime/WEEKNUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/WEEKNUM1904.php b/tests/data/Calculation/DateTime/WEEKNUM1904.php
index a8347f895..a70ebe756 100644
--- a/tests/data/Calculation/DateTime/WEEKNUM1904.php
+++ b/tests/data/Calculation/DateTime/WEEKNUM1904.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/WORKDAY.php b/tests/data/Calculation/DateTime/WORKDAY.php
index 7bb6a012a..f1d15424e 100644
--- a/tests/data/Calculation/DateTime/WORKDAY.php
+++ b/tests/data/Calculation/DateTime/WORKDAY.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/YEAR.php b/tests/data/Calculation/DateTime/YEAR.php
index bcb3e2bf1..d8bd37188 100644
--- a/tests/data/Calculation/DateTime/YEAR.php
+++ b/tests/data/Calculation/DateTime/YEAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/DateTime/YEARFRAC.php b/tests/data/Calculation/DateTime/YEARFRAC.php
index 13de34b4d..7613519c5 100644
--- a/tests/data/Calculation/DateTime/YEARFRAC.php
+++ b/tests/data/Calculation/DateTime/YEARFRAC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BESSELI.php b/tests/data/Calculation/Engineering/BESSELI.php
index c086f4fb6..f72640356 100644
--- a/tests/data/Calculation/Engineering/BESSELI.php
+++ b/tests/data/Calculation/Engineering/BESSELI.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BESSELJ.php b/tests/data/Calculation/Engineering/BESSELJ.php
index 943f91a8f..7f0f0908b 100644
--- a/tests/data/Calculation/Engineering/BESSELJ.php
+++ b/tests/data/Calculation/Engineering/BESSELJ.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BESSELK.php b/tests/data/Calculation/Engineering/BESSELK.php
index 431997ccf..507f82709 100644
--- a/tests/data/Calculation/Engineering/BESSELK.php
+++ b/tests/data/Calculation/Engineering/BESSELK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BESSELY.php b/tests/data/Calculation/Engineering/BESSELY.php
index fa2ca3cd3..006e74c66 100644
--- a/tests/data/Calculation/Engineering/BESSELY.php
+++ b/tests/data/Calculation/Engineering/BESSELY.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BIN2DEC.php b/tests/data/Calculation/Engineering/BIN2DEC.php
index d510d0bbc..48fa613e6 100644
--- a/tests/data/Calculation/Engineering/BIN2DEC.php
+++ b/tests/data/Calculation/Engineering/BIN2DEC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BIN2DECOpenOffice.php b/tests/data/Calculation/Engineering/BIN2DECOpenOffice.php
index 54fe1700a..1b26a8f04 100644
--- a/tests/data/Calculation/Engineering/BIN2DECOpenOffice.php
+++ b/tests/data/Calculation/Engineering/BIN2DECOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // Boolean okay for ODS, not for Excel/Gnumeric
     ['0', false], // Boolean okay for ODS, not for Excel/Gnumeric
diff --git a/tests/data/Calculation/Engineering/BIN2HEX.php b/tests/data/Calculation/Engineering/BIN2HEX.php
index ffb89706c..1cd240cdf 100644
--- a/tests/data/Calculation/Engineering/BIN2HEX.php
+++ b/tests/data/Calculation/Engineering/BIN2HEX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BIN2HEXOpenOffice.php b/tests/data/Calculation/Engineering/BIN2HEXOpenOffice.php
index 54fe1700a..1b26a8f04 100644
--- a/tests/data/Calculation/Engineering/BIN2HEXOpenOffice.php
+++ b/tests/data/Calculation/Engineering/BIN2HEXOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // Boolean okay for ODS, not for Excel/Gnumeric
     ['0', false], // Boolean okay for ODS, not for Excel/Gnumeric
diff --git a/tests/data/Calculation/Engineering/BIN2OCT.php b/tests/data/Calculation/Engineering/BIN2OCT.php
index bd656192d..55cddb61c 100644
--- a/tests/data/Calculation/Engineering/BIN2OCT.php
+++ b/tests/data/Calculation/Engineering/BIN2OCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BIN2OCTOpenOffice.php b/tests/data/Calculation/Engineering/BIN2OCTOpenOffice.php
index 54fe1700a..1b26a8f04 100644
--- a/tests/data/Calculation/Engineering/BIN2OCTOpenOffice.php
+++ b/tests/data/Calculation/Engineering/BIN2OCTOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // Boolean okay for ODS, not for Excel/Gnumeric
     ['0', false], // Boolean okay for ODS, not for Excel/Gnumeric
diff --git a/tests/data/Calculation/Engineering/BITAND.php b/tests/data/Calculation/Engineering/BITAND.php
index 4cfe42c06..a6608459d 100644
--- a/tests/data/Calculation/Engineering/BITAND.php
+++ b/tests/data/Calculation/Engineering/BITAND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BITLSHIFT.php b/tests/data/Calculation/Engineering/BITLSHIFT.php
index c63572408..b6059cd28 100644
--- a/tests/data/Calculation/Engineering/BITLSHIFT.php
+++ b/tests/data/Calculation/Engineering/BITLSHIFT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BITOR.php b/tests/data/Calculation/Engineering/BITOR.php
index 8f1c2290a..745c98224 100644
--- a/tests/data/Calculation/Engineering/BITOR.php
+++ b/tests/data/Calculation/Engineering/BITOR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BITRSHIFT.php b/tests/data/Calculation/Engineering/BITRSHIFT.php
index 08e46ea6b..9ddc2e83e 100644
--- a/tests/data/Calculation/Engineering/BITRSHIFT.php
+++ b/tests/data/Calculation/Engineering/BITRSHIFT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/BITXOR.php b/tests/data/Calculation/Engineering/BITXOR.php
index 2a538f155..ec886a6bd 100644
--- a/tests/data/Calculation/Engineering/BITXOR.php
+++ b/tests/data/Calculation/Engineering/BITXOR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/COMPLEX.php b/tests/data/Calculation/Engineering/COMPLEX.php
index 0979caa66..56f5f61df 100644
--- a/tests/data/Calculation/Engineering/COMPLEX.php
+++ b/tests/data/Calculation/Engineering/COMPLEX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/CONVERTUOM.php b/tests/data/Calculation/Engineering/CONVERTUOM.php
index c6f90c82a..7e74a4b98 100644
--- a/tests/data/Calculation/Engineering/CONVERTUOM.php
+++ b/tests/data/Calculation/Engineering/CONVERTUOM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/DEC2BIN.php b/tests/data/Calculation/Engineering/DEC2BIN.php
index 7d7bd0cfa..c3346af70 100644
--- a/tests/data/Calculation/Engineering/DEC2BIN.php
+++ b/tests/data/Calculation/Engineering/DEC2BIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/DEC2BINOpenOffice.php b/tests/data/Calculation/Engineering/DEC2BINOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/DEC2BINOpenOffice.php
+++ b/tests/data/Calculation/Engineering/DEC2BINOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/DEC2HEX.php b/tests/data/Calculation/Engineering/DEC2HEX.php
index 49a6683f6..2b9c708cc 100644
--- a/tests/data/Calculation/Engineering/DEC2HEX.php
+++ b/tests/data/Calculation/Engineering/DEC2HEX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/DEC2HEXOpenOffice.php b/tests/data/Calculation/Engineering/DEC2HEXOpenOffice.php
index b0972e3ce..bd2b7fe82 100644
--- a/tests/data/Calculation/Engineering/DEC2HEXOpenOffice.php
+++ b/tests/data/Calculation/Engineering/DEC2HEXOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts bool, Excel/Gnumeric do not
     ['0', false],
diff --git a/tests/data/Calculation/Engineering/DEC2OCT.php b/tests/data/Calculation/Engineering/DEC2OCT.php
index 400ffdec5..72cd06a90 100644
--- a/tests/data/Calculation/Engineering/DEC2OCT.php
+++ b/tests/data/Calculation/Engineering/DEC2OCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/DEC2OCTOpenOffice.php b/tests/data/Calculation/Engineering/DEC2OCTOpenOffice.php
index b0972e3ce..bd2b7fe82 100644
--- a/tests/data/Calculation/Engineering/DEC2OCTOpenOffice.php
+++ b/tests/data/Calculation/Engineering/DEC2OCTOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts bool, Excel/Gnumeric do not
     ['0', false],
diff --git a/tests/data/Calculation/Engineering/DELTA.php b/tests/data/Calculation/Engineering/DELTA.php
index d2e605b9f..df72447b8 100644
--- a/tests/data/Calculation/Engineering/DELTA.php
+++ b/tests/data/Calculation/Engineering/DELTA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/ERF.php b/tests/data/Calculation/Engineering/ERF.php
index 68fd0e4b5..5f7c82180 100644
--- a/tests/data/Calculation/Engineering/ERF.php
+++ b/tests/data/Calculation/Engineering/ERF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 //  Result, lower bound, upper bound,
diff --git a/tests/data/Calculation/Engineering/ERFC.php b/tests/data/Calculation/Engineering/ERFC.php
index 5bc85cf7d..259d493e6 100644
--- a/tests/data/Calculation/Engineering/ERFC.php
+++ b/tests/data/Calculation/Engineering/ERFC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 //  Result, x value
diff --git a/tests/data/Calculation/Engineering/ERFPRECISE.php b/tests/data/Calculation/Engineering/ERFPRECISE.php
index 0cc53abbc..ba902b970 100644
--- a/tests/data/Calculation/Engineering/ERFPRECISE.php
+++ b/tests/data/Calculation/Engineering/ERFPRECISE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 //  Result, lower bound, upper bound
 return [
     [0.0, 0],
diff --git a/tests/data/Calculation/Engineering/GESTEP.php b/tests/data/Calculation/Engineering/GESTEP.php
index 3d462df88..8ac1a467f 100644
--- a/tests/data/Calculation/Engineering/GESTEP.php
+++ b/tests/data/Calculation/Engineering/GESTEP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/HEX2BIN.php b/tests/data/Calculation/Engineering/HEX2BIN.php
index 130cad285..81f3a6428 100644
--- a/tests/data/Calculation/Engineering/HEX2BIN.php
+++ b/tests/data/Calculation/Engineering/HEX2BIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/HEX2BINOpenOffice.php b/tests/data/Calculation/Engineering/HEX2BINOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/HEX2BINOpenOffice.php
+++ b/tests/data/Calculation/Engineering/HEX2BINOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/HEX2DEC.php b/tests/data/Calculation/Engineering/HEX2DEC.php
index 965ac6d21..54c95ade9 100644
--- a/tests/data/Calculation/Engineering/HEX2DEC.php
+++ b/tests/data/Calculation/Engineering/HEX2DEC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/HEX2DECOpenOffice.php b/tests/data/Calculation/Engineering/HEX2DECOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/HEX2DECOpenOffice.php
+++ b/tests/data/Calculation/Engineering/HEX2DECOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/HEX2OCT.php b/tests/data/Calculation/Engineering/HEX2OCT.php
index 56047372f..713011b24 100644
--- a/tests/data/Calculation/Engineering/HEX2OCT.php
+++ b/tests/data/Calculation/Engineering/HEX2OCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/HEX2OCTOpenOffice.php b/tests/data/Calculation/Engineering/HEX2OCTOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/HEX2OCTOpenOffice.php
+++ b/tests/data/Calculation/Engineering/HEX2OCTOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/IMABS.php b/tests/data/Calculation/Engineering/IMABS.php
index 8e3a752aa..cb500608c 100644
--- a/tests/data/Calculation/Engineering/IMABS.php
+++ b/tests/data/Calculation/Engineering/IMABS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMAGINARY.php b/tests/data/Calculation/Engineering/IMAGINARY.php
index 149629164..e2ed7042d 100644
--- a/tests/data/Calculation/Engineering/IMAGINARY.php
+++ b/tests/data/Calculation/Engineering/IMAGINARY.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMARGUMENT.php b/tests/data/Calculation/Engineering/IMARGUMENT.php
index 6c8dc928e..65a0aa3b2 100644
--- a/tests/data/Calculation/Engineering/IMARGUMENT.php
+++ b/tests/data/Calculation/Engineering/IMARGUMENT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCONJUGATE.php b/tests/data/Calculation/Engineering/IMCONJUGATE.php
index ff9ae3418..ad5ba2652 100644
--- a/tests/data/Calculation/Engineering/IMCONJUGATE.php
+++ b/tests/data/Calculation/Engineering/IMCONJUGATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCOS.php b/tests/data/Calculation/Engineering/IMCOS.php
index 409b614ec..7a7f64c93 100644
--- a/tests/data/Calculation/Engineering/IMCOS.php
+++ b/tests/data/Calculation/Engineering/IMCOS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCOSH.php b/tests/data/Calculation/Engineering/IMCOSH.php
index b7458535e..308b48798 100644
--- a/tests/data/Calculation/Engineering/IMCOSH.php
+++ b/tests/data/Calculation/Engineering/IMCOSH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCOT.php b/tests/data/Calculation/Engineering/IMCOT.php
index 28dded62c..48055b1c0 100644
--- a/tests/data/Calculation/Engineering/IMCOT.php
+++ b/tests/data/Calculation/Engineering/IMCOT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCSC.php b/tests/data/Calculation/Engineering/IMCSC.php
index 9999c7bd2..2ead169d6 100644
--- a/tests/data/Calculation/Engineering/IMCSC.php
+++ b/tests/data/Calculation/Engineering/IMCSC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMCSCH.php b/tests/data/Calculation/Engineering/IMCSCH.php
index a293f49e6..7727aac0e 100644
--- a/tests/data/Calculation/Engineering/IMCSCH.php
+++ b/tests/data/Calculation/Engineering/IMCSCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMDIV.php b/tests/data/Calculation/Engineering/IMDIV.php
index 4c4b37191..179265eef 100644
--- a/tests/data/Calculation/Engineering/IMDIV.php
+++ b/tests/data/Calculation/Engineering/IMDIV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMEXP.php b/tests/data/Calculation/Engineering/IMEXP.php
index 8a00dc678..e360745e2 100644
--- a/tests/data/Calculation/Engineering/IMEXP.php
+++ b/tests/data/Calculation/Engineering/IMEXP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMLN.php b/tests/data/Calculation/Engineering/IMLN.php
index a74aed375..9f39964be 100644
--- a/tests/data/Calculation/Engineering/IMLN.php
+++ b/tests/data/Calculation/Engineering/IMLN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMLOG10.php b/tests/data/Calculation/Engineering/IMLOG10.php
index ac9957f94..7b6b4a2bf 100644
--- a/tests/data/Calculation/Engineering/IMLOG10.php
+++ b/tests/data/Calculation/Engineering/IMLOG10.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMLOG2.php b/tests/data/Calculation/Engineering/IMLOG2.php
index 5dd729e07..a68d04df2 100644
--- a/tests/data/Calculation/Engineering/IMLOG2.php
+++ b/tests/data/Calculation/Engineering/IMLOG2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMPOWER.php b/tests/data/Calculation/Engineering/IMPOWER.php
index 5a8bdf4e5..04296ca07 100644
--- a/tests/data/Calculation/Engineering/IMPOWER.php
+++ b/tests/data/Calculation/Engineering/IMPOWER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMPRODUCT.php b/tests/data/Calculation/Engineering/IMPRODUCT.php
index 9987ba69d..db60961db 100644
--- a/tests/data/Calculation/Engineering/IMPRODUCT.php
+++ b/tests/data/Calculation/Engineering/IMPRODUCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMREAL.php b/tests/data/Calculation/Engineering/IMREAL.php
index 2586f864e..65537d4bb 100644
--- a/tests/data/Calculation/Engineering/IMREAL.php
+++ b/tests/data/Calculation/Engineering/IMREAL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSEC.php b/tests/data/Calculation/Engineering/IMSEC.php
index 5e9e51284..2b7cc3cb4 100644
--- a/tests/data/Calculation/Engineering/IMSEC.php
+++ b/tests/data/Calculation/Engineering/IMSEC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSECH.php b/tests/data/Calculation/Engineering/IMSECH.php
index e7fd30cfc..13aa4f805 100644
--- a/tests/data/Calculation/Engineering/IMSECH.php
+++ b/tests/data/Calculation/Engineering/IMSECH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSIN.php b/tests/data/Calculation/Engineering/IMSIN.php
index b68b2e716..c45fd9413 100644
--- a/tests/data/Calculation/Engineering/IMSIN.php
+++ b/tests/data/Calculation/Engineering/IMSIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSINH.php b/tests/data/Calculation/Engineering/IMSINH.php
index 4545d5013..31ff84694 100644
--- a/tests/data/Calculation/Engineering/IMSINH.php
+++ b/tests/data/Calculation/Engineering/IMSINH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSQRT.php b/tests/data/Calculation/Engineering/IMSQRT.php
index 0b0259f3b..8a5cc1aa6 100644
--- a/tests/data/Calculation/Engineering/IMSQRT.php
+++ b/tests/data/Calculation/Engineering/IMSQRT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSUB.php b/tests/data/Calculation/Engineering/IMSUB.php
index 068558760..90f4c7462 100644
--- a/tests/data/Calculation/Engineering/IMSUB.php
+++ b/tests/data/Calculation/Engineering/IMSUB.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMSUM.php b/tests/data/Calculation/Engineering/IMSUM.php
index 25f877bdc..6b2dfa203 100644
--- a/tests/data/Calculation/Engineering/IMSUM.php
+++ b/tests/data/Calculation/Engineering/IMSUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/IMTAN.php b/tests/data/Calculation/Engineering/IMTAN.php
index 46fa35c9a..5b4d021b6 100644
--- a/tests/data/Calculation/Engineering/IMTAN.php
+++ b/tests/data/Calculation/Engineering/IMTAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/OCT2BIN.php b/tests/data/Calculation/Engineering/OCT2BIN.php
index 2ab74e71a..79da0e0ef 100644
--- a/tests/data/Calculation/Engineering/OCT2BIN.php
+++ b/tests/data/Calculation/Engineering/OCT2BIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/OCT2BINOpenOffice.php b/tests/data/Calculation/Engineering/OCT2BINOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/OCT2BINOpenOffice.php
+++ b/tests/data/Calculation/Engineering/OCT2BINOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/OCT2DEC.php b/tests/data/Calculation/Engineering/OCT2DEC.php
index caea03986..fb88a71f5 100644
--- a/tests/data/Calculation/Engineering/OCT2DEC.php
+++ b/tests/data/Calculation/Engineering/OCT2DEC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/OCT2DECOpenOffice.php b/tests/data/Calculation/Engineering/OCT2DECOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/OCT2DECOpenOffice.php
+++ b/tests/data/Calculation/Engineering/OCT2DECOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Engineering/OCT2HEX.php b/tests/data/Calculation/Engineering/OCT2HEX.php
index a6b5536f5..a8897989a 100644
--- a/tests/data/Calculation/Engineering/OCT2HEX.php
+++ b/tests/data/Calculation/Engineering/OCT2HEX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Engineering/OCT2HEXOpenOffice.php b/tests/data/Calculation/Engineering/OCT2HEXOpenOffice.php
index 31adb5f27..f0e268635 100644
--- a/tests/data/Calculation/Engineering/OCT2HEXOpenOffice.php
+++ b/tests/data/Calculation/Engineering/OCT2HEXOpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['1', true], // ODS accepts boolean, Excel/Gnumeric don't
     ['0', false], // ODS accepts boolean, Excel/Gnumeric don't
diff --git a/tests/data/Calculation/Financial/ACCRINT.php b/tests/data/Calculation/Financial/ACCRINT.php
index a7b508d16..d707b36ee 100644
--- a/tests/data/Calculation/Financial/ACCRINT.php
+++ b/tests/data/Calculation/Financial/ACCRINT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Issue date, 1st Interest, Settlement, Rate, Par, Freq, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/ACCRINTM.php b/tests/data/Calculation/Financial/ACCRINTM.php
index 444e41f90..8a9e1b122 100644
--- a/tests/data/Calculation/Financial/ACCRINTM.php
+++ b/tests/data/Calculation/Financial/ACCRINTM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Issue date, Settlement, Rate, Par, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/AMORDEGRC.php b/tests/data/Calculation/Financial/AMORDEGRC.php
index fa546c8cd..caaa29cc4 100644
--- a/tests/data/Calculation/Financial/AMORDEGRC.php
+++ b/tests/data/Calculation/Financial/AMORDEGRC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Cost, Date purchased, End of the 1st period, Salvage, Period, Depreciation, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/AMORLINC.php b/tests/data/Calculation/Financial/AMORLINC.php
index c01755368..d27c1b83d 100644
--- a/tests/data/Calculation/Financial/AMORLINC.php
+++ b/tests/data/Calculation/Financial/AMORLINC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Cost, Date purchased, End of the 1st period, Salvage, Period, Depreciation, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPDAYBS.php b/tests/data/Calculation/Financial/COUPDAYBS.php
index f41d3620c..8f8c873c5 100644
--- a/tests/data/Calculation/Financial/COUPDAYBS.php
+++ b/tests/data/Calculation/Financial/COUPDAYBS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPDAYS.php b/tests/data/Calculation/Financial/COUPDAYS.php
index caba56e55..50834c428 100644
--- a/tests/data/Calculation/Financial/COUPDAYS.php
+++ b/tests/data/Calculation/Financial/COUPDAYS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPDAYSNC.php b/tests/data/Calculation/Financial/COUPDAYSNC.php
index e8500263c..e3de4a6a0 100644
--- a/tests/data/Calculation/Financial/COUPDAYSNC.php
+++ b/tests/data/Calculation/Financial/COUPDAYSNC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPNCD.php b/tests/data/Calculation/Financial/COUPNCD.php
index d690525c9..e913ced01 100644
--- a/tests/data/Calculation/Financial/COUPNCD.php
+++ b/tests/data/Calculation/Financial/COUPNCD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPNUM.php b/tests/data/Calculation/Financial/COUPNUM.php
index 4cf0cc29b..f46c7c2d7 100644
--- a/tests/data/Calculation/Financial/COUPNUM.php
+++ b/tests/data/Calculation/Financial/COUPNUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/COUPPCD.php b/tests/data/Calculation/Financial/COUPPCD.php
index 88b93af5c..35ec8484c 100644
--- a/tests/data/Calculation/Financial/COUPPCD.php
+++ b/tests/data/Calculation/Financial/COUPPCD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Frequency, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/CUMIPMT.php b/tests/data/Calculation/Financial/CUMIPMT.php
index 2ccc5ff24..2e5deeab7 100644
--- a/tests/data/Calculation/Financial/CUMIPMT.php
+++ b/tests/data/Calculation/Financial/CUMIPMT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, nper, pv, start_period, end_period, type, result
 
 return [
diff --git a/tests/data/Calculation/Financial/CUMPRINC.php b/tests/data/Calculation/Financial/CUMPRINC.php
index e14d5adc1..684e65f45 100644
--- a/tests/data/Calculation/Financial/CUMPRINC.php
+++ b/tests/data/Calculation/Financial/CUMPRINC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, nper, pv, start_period, end_period, type, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DB.php b/tests/data/Calculation/Financial/DB.php
index 89bd22f2c..6e7ca02bf 100644
--- a/tests/data/Calculation/Financial/DB.php
+++ b/tests/data/Calculation/Financial/DB.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // cost, salvage, life, period, month, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DDB.php b/tests/data/Calculation/Financial/DDB.php
index 67962ea2e..7c6eb35d9 100644
--- a/tests/data/Calculation/Financial/DDB.php
+++ b/tests/data/Calculation/Financial/DDB.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // cost, salvage, life, period, month, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DISC.php b/tests/data/Calculation/Financial/DISC.php
index f33ed21bf..f301081d5 100644
--- a/tests/data/Calculation/Financial/DISC.php
+++ b/tests/data/Calculation/Financial/DISC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // settlement, maturity, price, redemption, basis, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DOLLARDE.php b/tests/data/Calculation/Financial/DOLLARDE.php
index 7f4c41952..0c9d82eec 100644
--- a/tests/data/Calculation/Financial/DOLLARDE.php
+++ b/tests/data/Calculation/Financial/DOLLARDE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // fractional_dollar, fraction, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DOLLARFR.php b/tests/data/Calculation/Financial/DOLLARFR.php
index 42ae133ec..e4b49ad49 100644
--- a/tests/data/Calculation/Financial/DOLLARFR.php
+++ b/tests/data/Calculation/Financial/DOLLARFR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // decimal_dollar, fraction, result
 
 return [
diff --git a/tests/data/Calculation/Financial/DaysPerYear.php b/tests/data/Calculation/Financial/DaysPerYear.php
index 2eb51a034..f49962cd9 100644
--- a/tests/data/Calculation/Financial/DaysPerYear.php
+++ b/tests/data/Calculation/Financial/DaysPerYear.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Financial\Constants as FinancialConstants;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
diff --git a/tests/data/Calculation/Financial/EFFECT.php b/tests/data/Calculation/Financial/EFFECT.php
index c81ca7f03..cd3a33638 100644
--- a/tests/data/Calculation/Financial/EFFECT.php
+++ b/tests/data/Calculation/Financial/EFFECT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // nominal_rate, npery, Result
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/data/Calculation/Financial/FV.php b/tests/data/Calculation/Financial/FV.php
index 4dce5373f..c7066df2e 100644
--- a/tests/data/Calculation/Financial/FV.php
+++ b/tests/data/Calculation/Financial/FV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, nper, pmt, pv, type, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/FVSCHEDULE.php b/tests/data/Calculation/Financial/FVSCHEDULE.php
index fde67411a..c2420b5df 100644
--- a/tests/data/Calculation/Financial/FVSCHEDULE.php
+++ b/tests/data/Calculation/Financial/FVSCHEDULE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // principal, schedule, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/INTRATE.php b/tests/data/Calculation/Financial/INTRATE.php
index 05e73c59f..7162e2f01 100644
--- a/tests/data/Calculation/Financial/INTRATE.php
+++ b/tests/data/Calculation/Financial/INTRATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Settlement, Maturity, Investment, Redemption, Basis, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/IPMT.php b/tests/data/Calculation/Financial/IPMT.php
index c8f66dea3..5d16c07fa 100644
--- a/tests/data/Calculation/Financial/IPMT.php
+++ b/tests/data/Calculation/Financial/IPMT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, per, nper, pv, fv, type, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/IRR.php b/tests/data/Calculation/Financial/IRR.php
index 5051182a5..7177995c1 100644
--- a/tests/data/Calculation/Financial/IRR.php
+++ b/tests/data/Calculation/Financial/IRR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // values, guess, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/ISPMT.php b/tests/data/Calculation/Financial/ISPMT.php
index 7209f1955..e2af00fde 100644
--- a/tests/data/Calculation/Financial/ISPMT.php
+++ b/tests/data/Calculation/Financial/ISPMT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, per, nper, pv, result
 
 return [
diff --git a/tests/data/Calculation/Financial/MIRR.php b/tests/data/Calculation/Financial/MIRR.php
index 460eb2072..d760982fd 100644
--- a/tests/data/Calculation/Financial/MIRR.php
+++ b/tests/data/Calculation/Financial/MIRR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // values, finance_rate, reinvestment_rate, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/NOMINAL.php b/tests/data/Calculation/Financial/NOMINAL.php
index aade7da09..d81147462 100644
--- a/tests/data/Calculation/Financial/NOMINAL.php
+++ b/tests/data/Calculation/Financial/NOMINAL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // effect_rate, npery, result
 
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
diff --git a/tests/data/Calculation/Financial/NPER.php b/tests/data/Calculation/Financial/NPER.php
index db53c501b..92030e667 100644
--- a/tests/data/Calculation/Financial/NPER.php
+++ b/tests/data/Calculation/Financial/NPER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, pmt, pv, fv, type, result
 
 return [
diff --git a/tests/data/Calculation/Financial/NPV.php b/tests/data/Calculation/Financial/NPV.php
index ac854269a..8977ef1db 100644
--- a/tests/data/Calculation/Financial/NPV.php
+++ b/tests/data/Calculation/Financial/NPV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // rate, values, result
 
 return [
diff --git a/tests/data/Calculation/Financial/PDURATION.php b/tests/data/Calculation/Financial/PDURATION.php
index e2ae67191..2a166062f 100644
--- a/tests/data/Calculation/Financial/PDURATION.php
+++ b/tests/data/Calculation/Financial/PDURATION.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         10.33803507,
diff --git a/tests/data/Calculation/Financial/PMT.php b/tests/data/Calculation/Financial/PMT.php
index ed1907deb..b805323c1 100644
--- a/tests/data/Calculation/Financial/PMT.php
+++ b/tests/data/Calculation/Financial/PMT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         -1037.032089359164,
diff --git a/tests/data/Calculation/Financial/PPMT.php b/tests/data/Calculation/Financial/PPMT.php
index 136e54791..972e056e2 100644
--- a/tests/data/Calculation/Financial/PPMT.php
+++ b/tests/data/Calculation/Financial/PPMT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         -75.623186008367,
diff --git a/tests/data/Calculation/Financial/PRICE.php b/tests/data/Calculation/Financial/PRICE.php
index f1f5c5077..4e9ad1307 100644
--- a/tests/data/Calculation/Financial/PRICE.php
+++ b/tests/data/Calculation/Financial/PRICE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Result, Settlement, Maturity, Rate, Yield, Redemption, Frequency, Basis
 
 return [
diff --git a/tests/data/Calculation/Financial/PRICE3.php b/tests/data/Calculation/Financial/PRICE3.php
index c5a5c07f1..90327ac5c 100644
--- a/tests/data/Calculation/Financial/PRICE3.php
+++ b/tests/data/Calculation/Financial/PRICE3.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Result, Settlement, Maturity, Rate, Yield, Redemption, Frequency, Basis
 // On the result line, the value is ODS's calculation.
 //     This agrees with Gnumeric, PhpSpreadsheet, and the published algorithm at:
diff --git a/tests/data/Calculation/Financial/PRICEDISC.php b/tests/data/Calculation/Financial/PRICEDISC.php
index bd3021a16..a71bfc3db 100644
--- a/tests/data/Calculation/Financial/PRICEDISC.php
+++ b/tests/data/Calculation/Financial/PRICEDISC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         90.0,
diff --git a/tests/data/Calculation/Financial/PRICEMAT.php b/tests/data/Calculation/Financial/PRICEMAT.php
index 433b523e2..93aab92a1 100644
--- a/tests/data/Calculation/Financial/PRICEMAT.php
+++ b/tests/data/Calculation/Financial/PRICEMAT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         99.98449887555694,
diff --git a/tests/data/Calculation/Financial/PV.php b/tests/data/Calculation/Financial/PV.php
index b0abf57a5..81ff88aa9 100644
--- a/tests/data/Calculation/Financial/PV.php
+++ b/tests/data/Calculation/Financial/PV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         -52990.70632392715,
diff --git a/tests/data/Calculation/Financial/RATE.php b/tests/data/Calculation/Financial/RATE.php
index f2026967b..f5a5ab492 100644
--- a/tests/data/Calculation/Financial/RATE.php
+++ b/tests/data/Calculation/Financial/RATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Periods, Payment, Present Value, Future Value, Type, Guess, Result
 
 return [
diff --git a/tests/data/Calculation/Financial/RECEIVED.php b/tests/data/Calculation/Financial/RECEIVED.php
index af183ba94..e16c06f1e 100644
--- a/tests/data/Calculation/Financial/RECEIVED.php
+++ b/tests/data/Calculation/Financial/RECEIVED.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1014584.6544071021,
diff --git a/tests/data/Calculation/Financial/RRI.php b/tests/data/Calculation/Financial/RRI.php
index d71211b5d..0318f45c7 100644
--- a/tests/data/Calculation/Financial/RRI.php
+++ b/tests/data/Calculation/Financial/RRI.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.04137974399241062,
diff --git a/tests/data/Calculation/Financial/SLN.php b/tests/data/Calculation/Financial/SLN.php
index f63120c19..766d64c72 100644
--- a/tests/data/Calculation/Financial/SLN.php
+++ b/tests/data/Calculation/Financial/SLN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1800,
diff --git a/tests/data/Calculation/Financial/SYD.php b/tests/data/Calculation/Financial/SYD.php
index a8dd078cb..9a0056e7f 100644
--- a/tests/data/Calculation/Financial/SYD.php
+++ b/tests/data/Calculation/Financial/SYD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3000,
diff --git a/tests/data/Calculation/Financial/TBILLEQ.php b/tests/data/Calculation/Financial/TBILLEQ.php
index 3624d171a..bacd1fa15 100644
--- a/tests/data/Calculation/Financial/TBILLEQ.php
+++ b/tests/data/Calculation/Financial/TBILLEQ.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Financial/TBILLPRICE.php b/tests/data/Calculation/Financial/TBILLPRICE.php
index 8a1bb85a4..720c0bfad 100644
--- a/tests/data/Calculation/Financial/TBILLPRICE.php
+++ b/tests/data/Calculation/Financial/TBILLPRICE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Financial/TBILLYIELD.php b/tests/data/Calculation/Financial/TBILLYIELD.php
index 30b417daf..244a7481c 100644
--- a/tests/data/Calculation/Financial/TBILLYIELD.php
+++ b/tests/data/Calculation/Financial/TBILLYIELD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Financial/USDOLLAR.php b/tests/data/Calculation/Financial/USDOLLAR.php
index 25cb4eae7..f5fbc1618 100644
--- a/tests/data/Calculation/Financial/USDOLLAR.php
+++ b/tests/data/Calculation/Financial/USDOLLAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['$12,345.67890', 12345.6789, 5],
 ];
diff --git a/tests/data/Calculation/Financial/XIRR.php b/tests/data/Calculation/Financial/XIRR.php
index 03bf6fee5..f22104c15 100644
--- a/tests/data/Calculation/Financial/XIRR.php
+++ b/tests/data/Calculation/Financial/XIRR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // result, message, values, dates, guess
 
 return [
diff --git a/tests/data/Calculation/Financial/XNPV.php b/tests/data/Calculation/Financial/XNPV.php
index 66e4d43e0..422e855dd 100644
--- a/tests/data/Calculation/Financial/XNPV.php
+++ b/tests/data/Calculation/Financial/XNPV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // result, message, rate, values, dates
 
 return [
diff --git a/tests/data/Calculation/Financial/YIELDDISC.php b/tests/data/Calculation/Financial/YIELDDISC.php
index d9ab1957a..b09f0c9fc 100644
--- a/tests/data/Calculation/Financial/YIELDDISC.php
+++ b/tests/data/Calculation/Financial/YIELDDISC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.05282257198685834,
diff --git a/tests/data/Calculation/Financial/YIELDMAT.php b/tests/data/Calculation/Financial/YIELDMAT.php
index 9980f4657..18eb9092e 100644
--- a/tests/data/Calculation/Financial/YIELDMAT.php
+++ b/tests/data/Calculation/Financial/YIELDMAT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.06095433369153867,
diff --git a/tests/data/Calculation/Functions/IF_CONDITION.php b/tests/data/Calculation/Functions/IF_CONDITION.php
index fce8c6410..b555f7ee0 100644
--- a/tests/data/Calculation/Functions/IF_CONDITION.php
+++ b/tests/data/Calculation/Functions/IF_CONDITION.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '<"A"',
diff --git a/tests/data/Calculation/FunctionsAsString.php b/tests/data/Calculation/FunctionsAsString.php
index 859534723..57606c1a1 100644
--- a/tests/data/Calculation/FunctionsAsString.php
+++ b/tests/data/Calculation/FunctionsAsString.php
@@ -1,24 +1,26 @@
 <?php
 
-    return [
-        // Note that these are meant to test the parser, not a comprehensive
-        // test of all Excel functions, which tests are handled elsewhere.
-        [6, '=SUM(1,2,3)'],
-        [60, '=SUM(A1:A3)'],
-        [70, '=SUM(A1,A2,A4)'],
-        [41, '=SUM(1,namedCell)'],
-        [50, '=A1+namedCell'],
-        [3, '=MATCH(6,{4,5,6,2},0)'],
-        ['#N/A', '=MATCH(8,{4,5,6,2},0)'],
-        [7, '=HLOOKUP(5,{1,5,10;2,6,11;3,7,12;4,8,13},3,FALSE)'],
-        ['Hello, World.', '=CONCATENATE("Hello, ", "World.")'],
-        ['{NON-EMPTY SET}', '=UPPER("{non-EMPTY set}")'], // braces not used for matrix
-        ['upper', '=LOWER(B1)'],
-        [false, '=and(B2,B3)'],
-        [0, '=acos(1)'],
-        [0.785398, '=round(atan({1,2,3}),6)'], // {1,2,3} will be flattened to 1
-        [2, '=minverse({-2.5,1.5;2,-1})'], // 2 is the flattened result of {2,3;4,5}
-        [4, '=MDETERM(MMULT({1,2;3,4},{5,6;7,8}))'], // multiple matrices
-        [110, '=SUM(A1,Sheet2!$A$1)'], // different sheet absolute address
-        [220, '=SUM(A2,A2B)'], // defined name on different sheet
-    ];
+declare(strict_types=1);
+
+return [
+    // Note that these are meant to test the parser, not a comprehensive
+    // test of all Excel functions, which tests are handled elsewhere.
+    [6, '=SUM(1,2,3)'],
+    [60, '=SUM(A1:A3)'],
+    [70, '=SUM(A1,A2,A4)'],
+    [41, '=SUM(1,namedCell)'],
+    [50, '=A1+namedCell'],
+    [3, '=MATCH(6,{4,5,6,2},0)'],
+    ['#N/A', '=MATCH(8,{4,5,6,2},0)'],
+    [7, '=HLOOKUP(5,{1,5,10;2,6,11;3,7,12;4,8,13},3,FALSE)'],
+    ['Hello, World.', '=CONCATENATE("Hello, ", "World.")'],
+    ['{NON-EMPTY SET}', '=UPPER("{non-EMPTY set}")'], // braces not used for matrix
+    ['upper', '=LOWER(B1)'],
+    [false, '=and(B2,B3)'],
+    [0, '=acos(1)'],
+    [0.785398, '=round(atan({1,2,3}),6)'], // {1,2,3} will be flattened to 1
+    [2, '=minverse({-2.5,1.5;2,-1})'], // 2 is the flattened result of {2,3;4,5}
+    [4, '=MDETERM(MMULT({1,2;3,4},{5,6;7,8}))'], // multiple matrices
+    [110, '=SUM(A1,Sheet2!$A$1)'], // different sheet absolute address
+    [220, '=SUM(A2,A2B)'], // defined name on different sheet
+];
diff --git a/tests/data/Calculation/Information/ERROR_TYPE.php b/tests/data/Calculation/Information/ERROR_TYPE.php
index 45f279704..3a3fb857b 100644
--- a/tests/data/Calculation/Information/ERROR_TYPE.php
+++ b/tests/data/Calculation/Information/ERROR_TYPE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#N/A',
diff --git a/tests/data/Calculation/Information/IS_BLANK.php b/tests/data/Calculation/Information/IS_BLANK.php
index c2c9aec18..a439b4dcf 100644
--- a/tests/data/Calculation/Information/IS_BLANK.php
+++ b/tests/data/Calculation/Information/IS_BLANK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         true,
diff --git a/tests/data/Calculation/Information/IS_ERR.php b/tests/data/Calculation/Information/IS_ERR.php
index 2e7373473..894be2714 100644
--- a/tests/data/Calculation/Information/IS_ERR.php
+++ b/tests/data/Calculation/Information/IS_ERR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/IS_ERROR.php b/tests/data/Calculation/Information/IS_ERROR.php
index 24e864fe9..39814fb94 100644
--- a/tests/data/Calculation/Information/IS_ERROR.php
+++ b/tests/data/Calculation/Information/IS_ERROR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/IS_EVEN.php b/tests/data/Calculation/Information/IS_EVEN.php
index ad009b58d..2bae50635 100644
--- a/tests/data/Calculation/Information/IS_EVEN.php
+++ b/tests/data/Calculation/Information/IS_EVEN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#NAME?',
diff --git a/tests/data/Calculation/Information/IS_LOGICAL.php b/tests/data/Calculation/Information/IS_LOGICAL.php
index e63fff9ba..fcc15db8d 100644
--- a/tests/data/Calculation/Information/IS_LOGICAL.php
+++ b/tests/data/Calculation/Information/IS_LOGICAL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/IS_NA.php b/tests/data/Calculation/Information/IS_NA.php
index c5ebdf798..672e777d3 100644
--- a/tests/data/Calculation/Information/IS_NA.php
+++ b/tests/data/Calculation/Information/IS_NA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/IS_NONTEXT.php b/tests/data/Calculation/Information/IS_NONTEXT.php
index 2fd5872c3..ccde83be3 100644
--- a/tests/data/Calculation/Information/IS_NONTEXT.php
+++ b/tests/data/Calculation/Information/IS_NONTEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         true,
diff --git a/tests/data/Calculation/Information/IS_NUMBER.php b/tests/data/Calculation/Information/IS_NUMBER.php
index a9e33453f..013f37f40 100644
--- a/tests/data/Calculation/Information/IS_NUMBER.php
+++ b/tests/data/Calculation/Information/IS_NUMBER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/IS_ODD.php b/tests/data/Calculation/Information/IS_ODD.php
index 890bd6a27..cb4536acf 100644
--- a/tests/data/Calculation/Information/IS_ODD.php
+++ b/tests/data/Calculation/Information/IS_ODD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#NAME?',
diff --git a/tests/data/Calculation/Information/IS_TEXT.php b/tests/data/Calculation/Information/IS_TEXT.php
index 998f8e27e..68022948d 100644
--- a/tests/data/Calculation/Information/IS_TEXT.php
+++ b/tests/data/Calculation/Information/IS_TEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Calculation/Information/N.php b/tests/data/Calculation/Information/N.php
index 3fc527da3..bac301592 100644
--- a/tests/data/Calculation/Information/N.php
+++ b/tests/data/Calculation/Information/N.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0,
diff --git a/tests/data/Calculation/Information/TYPE.php b/tests/data/Calculation/Information/TYPE.php
index c6aefb776..9cbc59dd3 100644
--- a/tests/data/Calculation/Information/TYPE.php
+++ b/tests/data/Calculation/Information/TYPE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/Logical/AND.php b/tests/data/Calculation/Logical/AND.php
index 3d08a3a6a..30a7e9d30 100644
--- a/tests/data/Calculation/Logical/AND.php
+++ b/tests/data/Calculation/Logical/AND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => [
         'exception',
diff --git a/tests/data/Calculation/Logical/ANDLiteral.php b/tests/data/Calculation/Logical/ANDLiteral.php
index 0dff483bb..0747f8a4a 100644
--- a/tests/data/Calculation/Logical/ANDLiteral.php
+++ b/tests/data/Calculation/Logical/ANDLiteral.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'both boolean true' => [true, 'true, true'],
     'boolean and string-true' => [true, 'true, "true"'],
diff --git a/tests/data/Calculation/Logical/IF.php b/tests/data/Calculation/Logical/IF.php
index 3bf7d90f2..1f69d1099 100644
--- a/tests/data/Calculation/Logical/IF.php
+++ b/tests/data/Calculation/Logical/IF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => [
         'exception',
diff --git a/tests/data/Calculation/Logical/IFERROR.php b/tests/data/Calculation/Logical/IFERROR.php
index a379a5fbf..ebc6b4060 100644
--- a/tests/data/Calculation/Logical/IFERROR.php
+++ b/tests/data/Calculation/Logical/IFERROR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'empty cell treated as 0' => [
         0,
diff --git a/tests/data/Calculation/Logical/IFNA.php b/tests/data/Calculation/Logical/IFNA.php
index d7fb7193f..4216212a0 100644
--- a/tests/data/Calculation/Logical/IFNA.php
+++ b/tests/data/Calculation/Logical/IFNA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         55,
diff --git a/tests/data/Calculation/Logical/IFS.php b/tests/data/Calculation/Logical/IFS.php
index d4dd607e4..2981e74c5 100644
--- a/tests/data/Calculation/Logical/IFS.php
+++ b/tests/data/Calculation/Logical/IFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => ['exception'],
     [
diff --git a/tests/data/Calculation/Logical/NOT.php b/tests/data/Calculation/Logical/NOT.php
index 9936c2681..37b94968d 100644
--- a/tests/data/Calculation/Logical/NOT.php
+++ b/tests/data/Calculation/Logical/NOT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => [
         'exception',
diff --git a/tests/data/Calculation/Logical/OR.php b/tests/data/Calculation/Logical/OR.php
index c5317b3bc..53aab1970 100644
--- a/tests/data/Calculation/Logical/OR.php
+++ b/tests/data/Calculation/Logical/OR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => [
         'exception',
diff --git a/tests/data/Calculation/Logical/ORLiteral.php b/tests/data/Calculation/Logical/ORLiteral.php
index 17f498822..d8331d60e 100644
--- a/tests/data/Calculation/Logical/ORLiteral.php
+++ b/tests/data/Calculation/Logical/ORLiteral.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'both boolean true' => [true, 'true, true'],
     'boolean or string-true' => [true, 'true, "true"'],
diff --git a/tests/data/Calculation/Logical/SWITCH.php b/tests/data/Calculation/Logical/SWITCH.php
index 689d1d8fa..724aa09db 100644
--- a/tests/data/Calculation/Logical/SWITCH.php
+++ b/tests/data/Calculation/Logical/SWITCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'match value1 A result is C' => [
         'C',
diff --git a/tests/data/Calculation/Logical/XOR.php b/tests/data/Calculation/Logical/XOR.php
index 57a170a48..52895d44b 100644
--- a/tests/data/Calculation/Logical/XOR.php
+++ b/tests/data/Calculation/Logical/XOR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => [
         'exception',
diff --git a/tests/data/Calculation/Logical/XORLiteral.php b/tests/data/Calculation/Logical/XORLiteral.php
index a0c0be707..086fb7e83 100644
--- a/tests/data/Calculation/Logical/XORLiteral.php
+++ b/tests/data/Calculation/Logical/XORLiteral.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'both boolean true' => [false, 'true, true'],
     'boolean xor string-true' => [false, 'true, "true"'],
diff --git a/tests/data/Calculation/LookupRef/ADDRESS.php b/tests/data/Calculation/LookupRef/ADDRESS.php
index 14a3cf7db..aaaada75a 100644
--- a/tests/data/Calculation/LookupRef/ADDRESS.php
+++ b/tests/data/Calculation/LookupRef/ADDRESS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '$C$2',
diff --git a/tests/data/Calculation/LookupRef/CHOOSE.php b/tests/data/Calculation/LookupRef/CHOOSE.php
index 96c297803..8d9ce259e 100644
--- a/tests/data/Calculation/LookupRef/CHOOSE.php
+++ b/tests/data/Calculation/LookupRef/CHOOSE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'brown',
diff --git a/tests/data/Calculation/LookupRef/COLUMN.php b/tests/data/Calculation/LookupRef/COLUMN.php
index f5119ba82..ae6e8ead9 100644
--- a/tests/data/Calculation/LookupRef/COLUMN.php
+++ b/tests/data/Calculation/LookupRef/COLUMN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/LookupRef/COLUMNS.php b/tests/data/Calculation/LookupRef/COLUMNS.php
index 3a6a587c4..09dd0ca76 100644
--- a/tests/data/Calculation/LookupRef/COLUMNS.php
+++ b/tests/data/Calculation/LookupRef/COLUMNS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/LookupRef/COLUMNSonSpreadsheet.php b/tests/data/Calculation/LookupRef/COLUMNSonSpreadsheet.php
index 4002c2f16..76505334b 100644
--- a/tests/data/Calculation/LookupRef/COLUMNSonSpreadsheet.php
+++ b/tests/data/Calculation/LookupRef/COLUMNSonSpreadsheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'global $e$2-$e$6' => [1, 'namedrangex'],
     'global $f$2:$h$2' => [3, 'namedrangey'],
diff --git a/tests/data/Calculation/LookupRef/COLUMNonSpreadsheet.php b/tests/data/Calculation/LookupRef/COLUMNonSpreadsheet.php
index cc93653e8..16a43707c 100644
--- a/tests/data/Calculation/LookupRef/COLUMNonSpreadsheet.php
+++ b/tests/data/Calculation/LookupRef/COLUMNonSpreadsheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'current column' => [2, 'omitted'],
     'global name $E$2:$E$6' => [5, 'namedrangex'],
diff --git a/tests/data/Calculation/LookupRef/FORMULATEXT.php b/tests/data/Calculation/LookupRef/FORMULATEXT.php
index 46639c28c..e5debe475 100644
--- a/tests/data/Calculation/LookupRef/FORMULATEXT.php
+++ b/tests/data/Calculation/LookupRef/FORMULATEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#N/A',
diff --git a/tests/data/Calculation/LookupRef/HLOOKUP.php b/tests/data/Calculation/LookupRef/HLOOKUP.php
index 29546426b..f822e99f8 100644
--- a/tests/data/Calculation/LookupRef/HLOOKUP.php
+++ b/tests/data/Calculation/LookupRef/HLOOKUP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 function orderGrid(): array
 {
     return [
diff --git a/tests/data/Calculation/LookupRef/HYPERLINK.php b/tests/data/Calculation/LookupRef/HYPERLINK.php
index 63ea4ed73..3e27ca46e 100644
--- a/tests/data/Calculation/LookupRef/HYPERLINK.php
+++ b/tests/data/Calculation/LookupRef/HYPERLINK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/LookupRef/INDEX.php b/tests/data/Calculation/LookupRef/INDEX.php
index 4d4d1dad2..47c0fc9f0 100644
--- a/tests/data/Calculation/LookupRef/INDEX.php
+++ b/tests/data/Calculation/LookupRef/INDEX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [20 => ['R' => 1]], // Expected
diff --git a/tests/data/Calculation/LookupRef/INDEXonSpreadsheet.php b/tests/data/Calculation/LookupRef/INDEXonSpreadsheet.php
index eff13722f..76f6ddd46 100644
--- a/tests/data/Calculation/LookupRef/INDEXonSpreadsheet.php
+++ b/tests/data/Calculation/LookupRef/INDEXonSpreadsheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'Single Cell' => [
         1, // Expected
diff --git a/tests/data/Calculation/LookupRef/INDIRECT.php b/tests/data/Calculation/LookupRef/INDIRECT.php
index 7dc2515a3..77554ec85 100644
--- a/tests/data/Calculation/LookupRef/INDIRECT.php
+++ b/tests/data/Calculation/LookupRef/INDIRECT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'cell range absolute' => [600, '$A$1:$A$3'],
     'cell range on different sheet' => [30, 'OtherSheet!A1:A2'],
diff --git a/tests/data/Calculation/LookupRef/LOOKUP.php b/tests/data/Calculation/LookupRef/LOOKUP.php
index 9c7d96eb0..84e3e2785 100644
--- a/tests/data/Calculation/LookupRef/LOOKUP.php
+++ b/tests/data/Calculation/LookupRef/LOOKUP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [ // Office reference example #1
         'orange',
diff --git a/tests/data/Calculation/LookupRef/MATCH.php b/tests/data/Calculation/LookupRef/MATCH.php
index 19d84a89d..02c9f0737 100644
--- a/tests/data/Calculation/LookupRef/MATCH.php
+++ b/tests/data/Calculation/LookupRef/MATCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'unsorted numeric array still finds match with type 1?' => [
         2, // Expected
diff --git a/tests/data/Calculation/LookupRef/OFFSET.php b/tests/data/Calculation/LookupRef/OFFSET.php
index 9c2f52c1d..53706dd1f 100644
--- a/tests/data/Calculation/LookupRef/OFFSET.php
+++ b/tests/data/Calculation/LookupRef/OFFSET.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#VALUE!',
diff --git a/tests/data/Calculation/LookupRef/ROW.php b/tests/data/Calculation/LookupRef/ROW.php
index d6092f7ff..55f02aecd 100644
--- a/tests/data/Calculation/LookupRef/ROW.php
+++ b/tests/data/Calculation/LookupRef/ROW.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/LookupRef/ROWS.php b/tests/data/Calculation/LookupRef/ROWS.php
index 938082996..c30f11d21 100644
--- a/tests/data/Calculation/LookupRef/ROWS.php
+++ b/tests/data/Calculation/LookupRef/ROWS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/LookupRef/ROWSonSpreadsheet.php b/tests/data/Calculation/LookupRef/ROWSonSpreadsheet.php
index 117885bc1..0c0936c86 100644
--- a/tests/data/Calculation/LookupRef/ROWSonSpreadsheet.php
+++ b/tests/data/Calculation/LookupRef/ROWSonSpreadsheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'global $E$2:$E$6' => [5, 'namedrangex'],
     'global $F$2:$H$2' => [1, 'namedrangey'],
diff --git a/tests/data/Calculation/LookupRef/ROWonSpreadsheet.php b/tests/data/Calculation/LookupRef/ROWonSpreadsheet.php
index f2395e6b7..0250934df 100644
--- a/tests/data/Calculation/LookupRef/ROWonSpreadsheet.php
+++ b/tests/data/Calculation/LookupRef/ROWonSpreadsheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'current row' => [3, 'omitted'],
     'global name $E$2:$E$6' => [2, 'namedrangex'],
diff --git a/tests/data/Calculation/LookupRef/TRANSPOSE.php b/tests/data/Calculation/LookupRef/TRANSPOSE.php
index a5ca45f48..1f75ff125 100644
--- a/tests/data/Calculation/LookupRef/TRANSPOSE.php
+++ b/tests/data/Calculation/LookupRef/TRANSPOSE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Calculation/LookupRef/VLOOKUP.php b/tests/data/Calculation/LookupRef/VLOOKUP.php
index 8ebbb2e9f..c2398f209 100644
--- a/tests/data/Calculation/LookupRef/VLOOKUP.php
+++ b/tests/data/Calculation/LookupRef/VLOOKUP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 function densityGrid(): array
 {
     return [
diff --git a/tests/data/Calculation/MathTrig/ABS.php b/tests/data/Calculation/MathTrig/ABS.php
index 4082ceebe..e64049808 100644
--- a/tests/data/Calculation/MathTrig/ABS.php
+++ b/tests/data/Calculation/MathTrig/ABS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception - not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/ACOS.php b/tests/data/Calculation/MathTrig/ACOS.php
index 487a0628a..ca4621873 100644
--- a/tests/data/Calculation/MathTrig/ACOS.php
+++ b/tests/data/Calculation/MathTrig/ACOS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/ACOSH.php b/tests/data/Calculation/MathTrig/ACOSH.php
index 9452be936..b5f391ac2 100644
--- a/tests/data/Calculation/MathTrig/ACOSH.php
+++ b/tests/data/Calculation/MathTrig/ACOSH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/ACOT.php b/tests/data/Calculation/MathTrig/ACOT.php
index 7d654c088..0a6432924 100644
--- a/tests/data/Calculation/MathTrig/ACOT.php
+++ b/tests/data/Calculation/MathTrig/ACOT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [3.04192400109863, -10],
diff --git a/tests/data/Calculation/MathTrig/ACOTH.php b/tests/data/Calculation/MathTrig/ACOTH.php
index cf5639b40..4f3d6383d 100644
--- a/tests/data/Calculation/MathTrig/ACOTH.php
+++ b/tests/data/Calculation/MathTrig/ACOTH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [-0.10033534773108, -10],
diff --git a/tests/data/Calculation/MathTrig/ARABIC.php b/tests/data/Calculation/MathTrig/ARABIC.php
index e2a6f46bf..f3dce71e4 100644
--- a/tests/data/Calculation/MathTrig/ARABIC.php
+++ b/tests/data/Calculation/MathTrig/ARABIC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0,
diff --git a/tests/data/Calculation/MathTrig/ASIN.php b/tests/data/Calculation/MathTrig/ASIN.php
index 1e874a859..9e20c0437 100644
--- a/tests/data/Calculation/MathTrig/ASIN.php
+++ b/tests/data/Calculation/MathTrig/ASIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/ASINH.php b/tests/data/Calculation/MathTrig/ASINH.php
index 27bf98e65..2455964e6 100644
--- a/tests/data/Calculation/MathTrig/ASINH.php
+++ b/tests/data/Calculation/MathTrig/ASINH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/ATAN.php b/tests/data/Calculation/MathTrig/ATAN.php
index 1b1fc4aeb..b9928e8ae 100644
--- a/tests/data/Calculation/MathTrig/ATAN.php
+++ b/tests/data/Calculation/MathTrig/ATAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/ATAN2.php b/tests/data/Calculation/MathTrig/ATAN2.php
index b4ec202f1..d8048bd15 100644
--- a/tests/data/Calculation/MathTrig/ATAN2.php
+++ b/tests/data/Calculation/MathTrig/ATAN2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // x_num, y_num, Result
 
 return [
diff --git a/tests/data/Calculation/MathTrig/ATANH.php b/tests/data/Calculation/MathTrig/ATANH.php
index e43a1bd0f..336b4074f 100644
--- a/tests/data/Calculation/MathTrig/ATANH.php
+++ b/tests/data/Calculation/MathTrig/ATANH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/BASE.php b/tests/data/Calculation/MathTrig/BASE.php
index 1f67fe2a8..b913f9aa4 100644
--- a/tests/data/Calculation/MathTrig/BASE.php
+++ b/tests/data/Calculation/MathTrig/BASE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '111',
diff --git a/tests/data/Calculation/MathTrig/CEILING.php b/tests/data/Calculation/MathTrig/CEILING.php
index a4af7df1c..c2adf59a6 100644
--- a/tests/data/Calculation/MathTrig/CEILING.php
+++ b/tests/data/Calculation/MathTrig/CEILING.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [3.0, '2.5, 1'],
     [-4.0, '-2.5, -2'],
diff --git a/tests/data/Calculation/MathTrig/CEILINGMATH.php b/tests/data/Calculation/MathTrig/CEILINGMATH.php
index ea50d6e1a..50734a974 100644
--- a/tests/data/Calculation/MathTrig/CEILINGMATH.php
+++ b/tests/data/Calculation/MathTrig/CEILINGMATH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [3, '2.5, 1'],
     [-2, '"-2.5", "-2"'],
diff --git a/tests/data/Calculation/MathTrig/CEILINGPRECISE.php b/tests/data/Calculation/MathTrig/CEILINGPRECISE.php
index dfeada23c..51bea6986 100644
--- a/tests/data/Calculation/MathTrig/CEILINGPRECISE.php
+++ b/tests/data/Calculation/MathTrig/CEILINGPRECISE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [3, '2.5, 1'],
     [-2, '-2.5, -2'],
diff --git a/tests/data/Calculation/MathTrig/COMBIN.php b/tests/data/Calculation/MathTrig/COMBIN.php
index d163e8836..a7044e275 100644
--- a/tests/data/Calculation/MathTrig/COMBIN.php
+++ b/tests/data/Calculation/MathTrig/COMBIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // NumObjs, NumInSet, Result
 
 return [
diff --git a/tests/data/Calculation/MathTrig/COMBINA.php b/tests/data/Calculation/MathTrig/COMBINA.php
index c5a26a5f2..bc81207be 100644
--- a/tests/data/Calculation/MathTrig/COMBINA.php
+++ b/tests/data/Calculation/MathTrig/COMBINA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // NumObjs, NumInSet, Result
 
 return [
diff --git a/tests/data/Calculation/MathTrig/COS.php b/tests/data/Calculation/MathTrig/COS.php
index 9254fe58c..497b903f7 100644
--- a/tests/data/Calculation/MathTrig/COS.php
+++ b/tests/data/Calculation/MathTrig/COS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/COSH.php b/tests/data/Calculation/MathTrig/COSH.php
index 7057e9212..09d2e7872 100644
--- a/tests/data/Calculation/MathTrig/COSH.php
+++ b/tests/data/Calculation/MathTrig/COSH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/COT.php b/tests/data/Calculation/MathTrig/COT.php
index 497acac9d..19d63eb21 100644
--- a/tests/data/Calculation/MathTrig/COT.php
+++ b/tests/data/Calculation/MathTrig/COT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [-1.54235104535692, -10],
diff --git a/tests/data/Calculation/MathTrig/COTH.php b/tests/data/Calculation/MathTrig/COTH.php
index 218292d28..804f01c76 100644
--- a/tests/data/Calculation/MathTrig/COTH.php
+++ b/tests/data/Calculation/MathTrig/COTH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [-1.00000000412231, -10],
diff --git a/tests/data/Calculation/MathTrig/CSC.php b/tests/data/Calculation/MathTrig/CSC.php
index 54d974487..1a8213735 100644
--- a/tests/data/Calculation/MathTrig/CSC.php
+++ b/tests/data/Calculation/MathTrig/CSC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [1.83816396088967, -10],
diff --git a/tests/data/Calculation/MathTrig/CSCH.php b/tests/data/Calculation/MathTrig/CSCH.php
index c94a013f4..3e6304c45 100644
--- a/tests/data/Calculation/MathTrig/CSCH.php
+++ b/tests/data/Calculation/MathTrig/CSCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [-0.00009079985971, -10],
diff --git a/tests/data/Calculation/MathTrig/DEGREES.php b/tests/data/Calculation/MathTrig/DEGREES.php
index 04be2d825..5aa78f9de 100644
--- a/tests/data/Calculation/MathTrig/DEGREES.php
+++ b/tests/data/Calculation/MathTrig/DEGREES.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/EVEN.php b/tests/data/Calculation/MathTrig/EVEN.php
index ff44f0d6c..9f8160ebe 100644
--- a/tests/data/Calculation/MathTrig/EVEN.php
+++ b/tests/data/Calculation/MathTrig/EVEN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0, 'null'],
     [6, 5.4],
diff --git a/tests/data/Calculation/MathTrig/EXP.php b/tests/data/Calculation/MathTrig/EXP.php
index f9845ea3a..8eade8dbb 100644
--- a/tests/data/Calculation/MathTrig/EXP.php
+++ b/tests/data/Calculation/MathTrig/EXP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/FACT.php b/tests/data/Calculation/MathTrig/FACT.php
index c789ced8b..20175e0d6 100644
--- a/tests/data/Calculation/MathTrig/FACT.php
+++ b/tests/data/Calculation/MathTrig/FACT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         120,
diff --git a/tests/data/Calculation/MathTrig/FACTDOUBLE.php b/tests/data/Calculation/MathTrig/FACTDOUBLE.php
index 34a3403f9..e5e8fd8ad 100644
--- a/tests/data/Calculation/MathTrig/FACTDOUBLE.php
+++ b/tests/data/Calculation/MathTrig/FACTDOUBLE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/MathTrig/FACTGNUMERIC.php b/tests/data/Calculation/MathTrig/FACTGNUMERIC.php
index 0f040dd02..de70cf17e 100644
--- a/tests/data/Calculation/MathTrig/FACTGNUMERIC.php
+++ b/tests/data/Calculation/MathTrig/FACTGNUMERIC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         120,
diff --git a/tests/data/Calculation/MathTrig/FLOOR.php b/tests/data/Calculation/MathTrig/FLOOR.php
index 442f7c9f4..ec2aa87f8 100644
--- a/tests/data/Calculation/MathTrig/FLOOR.php
+++ b/tests/data/Calculation/MathTrig/FLOOR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [2, '2.5, 1'],
     [-2, '-2.5, -2'],
diff --git a/tests/data/Calculation/MathTrig/FLOORMATH.php b/tests/data/Calculation/MathTrig/FLOORMATH.php
index e871c5295..d8b1303fb 100644
--- a/tests/data/Calculation/MathTrig/FLOORMATH.php
+++ b/tests/data/Calculation/MathTrig/FLOORMATH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [2, '2.5, 1'],
     [-4, '"-2.5", "-2"'],
diff --git a/tests/data/Calculation/MathTrig/FLOORPRECISE.php b/tests/data/Calculation/MathTrig/FLOORPRECISE.php
index 8cc2c0432..73f13ceb2 100644
--- a/tests/data/Calculation/MathTrig/FLOORPRECISE.php
+++ b/tests/data/Calculation/MathTrig/FLOORPRECISE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [2, '2.5, 1'],
     [-4, '-2.5, -2'],
diff --git a/tests/data/Calculation/MathTrig/GCD.php b/tests/data/Calculation/MathTrig/GCD.php
index 7ace4bc67..016f24fe7 100644
--- a/tests/data/Calculation/MathTrig/GCD.php
+++ b/tests/data/Calculation/MathTrig/GCD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/Calculation/MathTrig/INT.php b/tests/data/Calculation/MathTrig/INT.php
index ee6740f77..09ce75918 100644
--- a/tests/data/Calculation/MathTrig/INT.php
+++ b/tests/data/Calculation/MathTrig/INT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     [5, '5.4'],
diff --git a/tests/data/Calculation/MathTrig/LCM.php b/tests/data/Calculation/MathTrig/LCM.php
index 92a891756..995921d74 100644
--- a/tests/data/Calculation/MathTrig/LCM.php
+++ b/tests/data/Calculation/MathTrig/LCM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         10,
diff --git a/tests/data/Calculation/MathTrig/LN.php b/tests/data/Calculation/MathTrig/LN.php
index 3bcd8b6c8..197381a19 100644
--- a/tests/data/Calculation/MathTrig/LN.php
+++ b/tests/data/Calculation/MathTrig/LN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/LOG.php b/tests/data/Calculation/MathTrig/LOG.php
index 4e52e8759..43013f303 100644
--- a/tests/data/Calculation/MathTrig/LOG.php
+++ b/tests/data/Calculation/MathTrig/LOG.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // number, base, result
 
 return [
diff --git a/tests/data/Calculation/MathTrig/LOG10.php b/tests/data/Calculation/MathTrig/LOG10.php
index 72869559a..8afc2cc35 100644
--- a/tests/data/Calculation/MathTrig/LOG10.php
+++ b/tests/data/Calculation/MathTrig/LOG10.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/MDETERM.php b/tests/data/Calculation/MathTrig/MDETERM.php
index b26d04d73..076b1e46f 100644
--- a/tests/data/Calculation/MathTrig/MDETERM.php
+++ b/tests/data/Calculation/MathTrig/MDETERM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0,
diff --git a/tests/data/Calculation/MathTrig/MINVERSE.php b/tests/data/Calculation/MathTrig/MINVERSE.php
index 89feae1ae..99a39ce39 100644
--- a/tests/data/Calculation/MathTrig/MINVERSE.php
+++ b/tests/data/Calculation/MathTrig/MINVERSE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Calculation/MathTrig/MMULT.php b/tests/data/Calculation/MathTrig/MMULT.php
index 7b424d589..c50cc8f27 100644
--- a/tests/data/Calculation/MathTrig/MMULT.php
+++ b/tests/data/Calculation/MathTrig/MMULT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Calculation/MathTrig/MOD.php b/tests/data/Calculation/MathTrig/MOD.php
index e53383d1b..dafc016bc 100644
--- a/tests/data/Calculation/MathTrig/MOD.php
+++ b/tests/data/Calculation/MathTrig/MOD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/MathTrig/MROUND.php b/tests/data/Calculation/MathTrig/MROUND.php
index aeb8c1d67..9a7384010 100644
--- a/tests/data/Calculation/MathTrig/MROUND.php
+++ b/tests/data/Calculation/MathTrig/MROUND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [9, '10,3'],
     [-9, '-10,-3'],
diff --git a/tests/data/Calculation/MathTrig/MULTINOMIAL.php b/tests/data/Calculation/MathTrig/MULTINOMIAL.php
index e56d341d3..eabb68d15 100644
--- a/tests/data/Calculation/MathTrig/MULTINOMIAL.php
+++ b/tests/data/Calculation/MathTrig/MULTINOMIAL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1260,
diff --git a/tests/data/Calculation/MathTrig/ODD.php b/tests/data/Calculation/MathTrig/ODD.php
index ae1806775..7c1abfa87 100644
--- a/tests/data/Calculation/MathTrig/ODD.php
+++ b/tests/data/Calculation/MathTrig/ODD.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [1, 'null'],
     [7, 5.4],
diff --git a/tests/data/Calculation/MathTrig/POWER.php b/tests/data/Calculation/MathTrig/POWER.php
index 16c8c2efe..a89e202d2 100644
--- a/tests/data/Calculation/MathTrig/POWER.php
+++ b/tests/data/Calculation/MathTrig/POWER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#NUM!',
diff --git a/tests/data/Calculation/MathTrig/PRODUCT.php b/tests/data/Calculation/MathTrig/PRODUCT.php
index 657c713c0..67e36ee51 100644
--- a/tests/data/Calculation/MathTrig/PRODUCT.php
+++ b/tests/data/Calculation/MathTrig/PRODUCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2250,
diff --git a/tests/data/Calculation/MathTrig/QUOTIENT.php b/tests/data/Calculation/MathTrig/QUOTIENT.php
index 4190bde65..1ba0f5eef 100644
--- a/tests/data/Calculation/MathTrig/QUOTIENT.php
+++ b/tests/data/Calculation/MathTrig/QUOTIENT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/MathTrig/RADIANS.php b/tests/data/Calculation/MathTrig/RADIANS.php
index 9d03b8d95..517ff57bf 100644
--- a/tests/data/Calculation/MathTrig/RADIANS.php
+++ b/tests/data/Calculation/MathTrig/RADIANS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/RANDBETWEEN.php b/tests/data/Calculation/MathTrig/RANDBETWEEN.php
index 4278b67af..758400d4f 100644
--- a/tests/data/Calculation/MathTrig/RANDBETWEEN.php
+++ b/tests/data/Calculation/MathTrig/RANDBETWEEN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', 'y', 3],
     ['#VALUE!', 3, 'y'],
diff --git a/tests/data/Calculation/MathTrig/ROMAN.php b/tests/data/Calculation/MathTrig/ROMAN.php
index d73868ca6..130dc717e 100644
--- a/tests/data/Calculation/MathTrig/ROMAN.php
+++ b/tests/data/Calculation/MathTrig/ROMAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['XLIX', '49'],
     ['L', '50'],
diff --git a/tests/data/Calculation/MathTrig/ROUND.php b/tests/data/Calculation/MathTrig/ROUND.php
index 4cdc02f22..3a2d0a2f0 100644
--- a/tests/data/Calculation/MathTrig/ROUND.php
+++ b/tests/data/Calculation/MathTrig/ROUND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0, '0,2'],
     [663, '662.79, 0'],
diff --git a/tests/data/Calculation/MathTrig/ROUNDDOWN.php b/tests/data/Calculation/MathTrig/ROUNDDOWN.php
index 5881aa0ee..3a65c13f2 100644
--- a/tests/data/Calculation/MathTrig/ROUNDDOWN.php
+++ b/tests/data/Calculation/MathTrig/ROUNDDOWN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0, '0,2'],
     [662, '662.79,0'],
diff --git a/tests/data/Calculation/MathTrig/ROUNDUP.php b/tests/data/Calculation/MathTrig/ROUNDUP.php
index 07c5eacbb..9014a9e3c 100644
--- a/tests/data/Calculation/MathTrig/ROUNDUP.php
+++ b/tests/data/Calculation/MathTrig/ROUNDUP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0, '0,2'],
     [663, '662.79, 0'],
diff --git a/tests/data/Calculation/MathTrig/SEC.php b/tests/data/Calculation/MathTrig/SEC.php
index 13dcd5b22..c46ff697b 100644
--- a/tests/data/Calculation/MathTrig/SEC.php
+++ b/tests/data/Calculation/MathTrig/SEC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [-1.1917935066879, -10],
diff --git a/tests/data/Calculation/MathTrig/SECH.php b/tests/data/Calculation/MathTrig/SECH.php
index 38bb128ec..7e3887bda 100644
--- a/tests/data/Calculation/MathTrig/SECH.php
+++ b/tests/data/Calculation/MathTrig/SECH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['#VALUE!', '"ABC"'],
     [0.00009079985934, -10],
diff --git a/tests/data/Calculation/MathTrig/SEQUENCE.php b/tests/data/Calculation/MathTrig/SEQUENCE.php
index 49c901022..6ae7fb433 100644
--- a/tests/data/Calculation/MathTrig/SEQUENCE.php
+++ b/tests/data/Calculation/MathTrig/SEQUENCE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [2, 2],
diff --git a/tests/data/Calculation/MathTrig/SERIESSUM.php b/tests/data/Calculation/MathTrig/SERIESSUM.php
index 2163dab74..66df98b83 100644
--- a/tests/data/Calculation/MathTrig/SERIESSUM.php
+++ b/tests/data/Calculation/MathTrig/SERIESSUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3905,
diff --git a/tests/data/Calculation/MathTrig/SIGN.php b/tests/data/Calculation/MathTrig/SIGN.php
index fab57c808..91da4e2c8 100644
--- a/tests/data/Calculation/MathTrig/SIGN.php
+++ b/tests/data/Calculation/MathTrig/SIGN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [-1, -1.5],
     [-1, -1],
diff --git a/tests/data/Calculation/MathTrig/SIN.php b/tests/data/Calculation/MathTrig/SIN.php
index 7518aae2d..62455b4a0 100644
--- a/tests/data/Calculation/MathTrig/SIN.php
+++ b/tests/data/Calculation/MathTrig/SIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/SINH.php b/tests/data/Calculation/MathTrig/SINH.php
index 7d9091440..f856f2c1c 100644
--- a/tests/data/Calculation/MathTrig/SINH.php
+++ b/tests/data/Calculation/MathTrig/SINH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/SQRT.php b/tests/data/Calculation/MathTrig/SQRT.php
index f54038f81..79fb417e8 100644
--- a/tests/data/Calculation/MathTrig/SQRT.php
+++ b/tests/data/Calculation/MathTrig/SQRT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception'], // exception not enough args
     ['#VALUE!', 'ABC'],
diff --git a/tests/data/Calculation/MathTrig/SQRTPI.php b/tests/data/Calculation/MathTrig/SQRTPI.php
index 9f4c057f4..49190fdf9 100644
--- a/tests/data/Calculation/MathTrig/SQRTPI.php
+++ b/tests/data/Calculation/MathTrig/SQRTPI.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#VALUE!',
diff --git a/tests/data/Calculation/MathTrig/SUBTOTAL.php b/tests/data/Calculation/MathTrig/SUBTOTAL.php
index 8ba16df25..64e44f423 100644
--- a/tests/data/Calculation/MathTrig/SUBTOTAL.php
+++ b/tests/data/Calculation/MathTrig/SUBTOTAL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [19.3333333333333, 1],
     [12, 2],
diff --git a/tests/data/Calculation/MathTrig/SUBTOTALHIDDEN.php b/tests/data/Calculation/MathTrig/SUBTOTALHIDDEN.php
index df6375dcc..f12a07a05 100644
--- a/tests/data/Calculation/MathTrig/SUBTOTALHIDDEN.php
+++ b/tests/data/Calculation/MathTrig/SUBTOTALHIDDEN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [21, 101],
     [5, 102],
diff --git a/tests/data/Calculation/MathTrig/SUM.php b/tests/data/Calculation/MathTrig/SUM.php
index ad2c78e0c..f3c5c265f 100644
--- a/tests/data/Calculation/MathTrig/SUM.php
+++ b/tests/data/Calculation/MathTrig/SUM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [50, 5, 15, 30],
     [52, 5, 15, 30, 2],
diff --git a/tests/data/Calculation/MathTrig/SUMIF.php b/tests/data/Calculation/MathTrig/SUMIF.php
index bb5d6aa12..ff9dd4dfa 100644
--- a/tests/data/Calculation/MathTrig/SUMIF.php
+++ b/tests/data/Calculation/MathTrig/SUMIF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         15,
diff --git a/tests/data/Calculation/MathTrig/SUMIFS.php b/tests/data/Calculation/MathTrig/SUMIFS.php
index 9d860c30a..2e3ab0a26 100644
--- a/tests/data/Calculation/MathTrig/SUMIFS.php
+++ b/tests/data/Calculation/MathTrig/SUMIFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0,
diff --git a/tests/data/Calculation/MathTrig/SUMLITERALS.php b/tests/data/Calculation/MathTrig/SUMLITERALS.php
index 0ea593861..8c1a6df35 100644
--- a/tests/data/Calculation/MathTrig/SUMLITERALS.php
+++ b/tests/data/Calculation/MathTrig/SUMLITERALS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [50, '5, 15, 30'],
     [52, '5, 15, 30, 2'],
diff --git a/tests/data/Calculation/MathTrig/SUMPRODUCT.php b/tests/data/Calculation/MathTrig/SUMPRODUCT.php
index 14ea8b397..06a3e7def 100644
--- a/tests/data/Calculation/MathTrig/SUMPRODUCT.php
+++ b/tests/data/Calculation/MathTrig/SUMPRODUCT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         29,
diff --git a/tests/data/Calculation/MathTrig/SUMSQ.php b/tests/data/Calculation/MathTrig/SUMSQ.php
index f62e802a4..96869c0f6 100644
--- a/tests/data/Calculation/MathTrig/SUMSQ.php
+++ b/tests/data/Calculation/MathTrig/SUMSQ.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         25,
diff --git a/tests/data/Calculation/MathTrig/SUMWITHINDEXMATCH.php b/tests/data/Calculation/MathTrig/SUMWITHINDEXMATCH.php
index 35555830e..db7685d6e 100644
--- a/tests/data/Calculation/MathTrig/SUMWITHINDEXMATCH.php
+++ b/tests/data/Calculation/MathTrig/SUMWITHINDEXMATCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         64, '=SUM(4 * INDEX(Lookup!B2, MATCH(A2, Lookup!A2, 0)))',
diff --git a/tests/data/Calculation/MathTrig/SUMX2MY2.php b/tests/data/Calculation/MathTrig/SUMX2MY2.php
index 725910f18..f5badc8c5 100644
--- a/tests/data/Calculation/MathTrig/SUMX2MY2.php
+++ b/tests/data/Calculation/MathTrig/SUMX2MY2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         12,
diff --git a/tests/data/Calculation/MathTrig/SUMX2PY2.php b/tests/data/Calculation/MathTrig/SUMX2PY2.php
index 68d0ebf79..1ddd64d34 100644
--- a/tests/data/Calculation/MathTrig/SUMX2PY2.php
+++ b/tests/data/Calculation/MathTrig/SUMX2PY2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         64,
diff --git a/tests/data/Calculation/MathTrig/SUMXMY2.php b/tests/data/Calculation/MathTrig/SUMXMY2.php
index 0a7724db9..cbae0efff 100644
--- a/tests/data/Calculation/MathTrig/SUMXMY2.php
+++ b/tests/data/Calculation/MathTrig/SUMXMY2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         6,
diff --git a/tests/data/Calculation/MathTrig/TAN.php b/tests/data/Calculation/MathTrig/TAN.php
index 9b5e4f740..cbba7ee30 100644
--- a/tests/data/Calculation/MathTrig/TAN.php
+++ b/tests/data/Calculation/MathTrig/TAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/TANH.php b/tests/data/Calculation/MathTrig/TANH.php
index 8b8d428bd..0721b1b5b 100644
--- a/tests/data/Calculation/MathTrig/TANH.php
+++ b/tests/data/Calculation/MathTrig/TANH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['exception', ''],
     ['#VALUE!', '"ABC"'],
diff --git a/tests/data/Calculation/MathTrig/TRUNC.php b/tests/data/Calculation/MathTrig/TRUNC.php
index f24c38bd8..40fa52160 100644
--- a/tests/data/Calculation/MathTrig/TRUNC.php
+++ b/tests/data/Calculation/MathTrig/TRUNC.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [3.14, '3.14159, 2'],
     [3.141, '3.14159,  3'],
diff --git a/tests/data/Calculation/Statistical/AVEDEV.php b/tests/data/Calculation/Statistical/AVEDEV.php
index 7ae7360a0..c7968c3d9 100644
--- a/tests/data/Calculation/Statistical/AVEDEV.php
+++ b/tests/data/Calculation/Statistical/AVEDEV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1.020408163265,
diff --git a/tests/data/Calculation/Statistical/AVERAGE.php b/tests/data/Calculation/Statistical/AVERAGE.php
index 0cd8c4a70..dccd6fef7 100644
--- a/tests/data/Calculation/Statistical/AVERAGE.php
+++ b/tests/data/Calculation/Statistical/AVERAGE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         11,
diff --git a/tests/data/Calculation/Statistical/AVERAGEA.php b/tests/data/Calculation/Statistical/AVERAGEA.php
index bb5e192c3..407f28f2b 100644
--- a/tests/data/Calculation/Statistical/AVERAGEA.php
+++ b/tests/data/Calculation/Statistical/AVERAGEA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         7.0,
diff --git a/tests/data/Calculation/Statistical/AVERAGEIF.php b/tests/data/Calculation/Statistical/AVERAGEIF.php
index 736b833fa..1c3848deb 100644
--- a/tests/data/Calculation/Statistical/AVERAGEIF.php
+++ b/tests/data/Calculation/Statistical/AVERAGEIF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         14000,
diff --git a/tests/data/Calculation/Statistical/AVERAGEIFS.php b/tests/data/Calculation/Statistical/AVERAGEIFS.php
index 8c62a0953..46c16ecd0 100644
--- a/tests/data/Calculation/Statistical/AVERAGEIFS.php
+++ b/tests/data/Calculation/Statistical/AVERAGEIFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no argument' => [
         'exception',
diff --git a/tests/data/Calculation/Statistical/BETADIST.php b/tests/data/Calculation/Statistical/BETADIST.php
index ef89575fd..92b61fc5a 100644
--- a/tests/data/Calculation/Statistical/BETADIST.php
+++ b/tests/data/Calculation/Statistical/BETADIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.4059136,
diff --git a/tests/data/Calculation/Statistical/BETAINV.php b/tests/data/Calculation/Statistical/BETAINV.php
index 609c28049..378dd9197 100644
--- a/tests/data/Calculation/Statistical/BETAINV.php
+++ b/tests/data/Calculation/Statistical/BETAINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1.862243320728,
diff --git a/tests/data/Calculation/Statistical/BINOMDIST.php b/tests/data/Calculation/Statistical/BINOMDIST.php
index 3606bced5..e49072925 100644
--- a/tests/data/Calculation/Statistical/BINOMDIST.php
+++ b/tests/data/Calculation/Statistical/BINOMDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.706399436132,
diff --git a/tests/data/Calculation/Statistical/BINOMDISTRANGE.php b/tests/data/Calculation/Statistical/BINOMDISTRANGE.php
index 153706d15..56b2d315a 100644
--- a/tests/data/Calculation/Statistical/BINOMDISTRANGE.php
+++ b/tests/data/Calculation/Statistical/BINOMDISTRANGE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.083974967429,
diff --git a/tests/data/Calculation/Statistical/BINOMINV.php b/tests/data/Calculation/Statistical/BINOMINV.php
index 2f73e29b0..b3d2446d8 100644
--- a/tests/data/Calculation/Statistical/BINOMINV.php
+++ b/tests/data/Calculation/Statistical/BINOMINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         32,
diff --git a/tests/data/Calculation/Statistical/BasicCOUNT.php b/tests/data/Calculation/Statistical/BasicCOUNT.php
index 4e1d31b06..ab7107835 100644
--- a/tests/data/Calculation/Statistical/BasicCOUNT.php
+++ b/tests/data/Calculation/Statistical/BasicCOUNT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Shared\Date;
 
 return [
diff --git a/tests/data/Calculation/Statistical/CHIDISTLeftTail.php b/tests/data/Calculation/Statistical/CHIDISTLeftTail.php
index 313061ac9..a400b254c 100644
--- a/tests/data/Calculation/Statistical/CHIDISTLeftTail.php
+++ b/tests/data/Calculation/Statistical/CHIDISTLeftTail.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.520499877813,
diff --git a/tests/data/Calculation/Statistical/CHIDISTRightTail.php b/tests/data/Calculation/Statistical/CHIDISTRightTail.php
index 24ddab9f8..51293a36f 100644
--- a/tests/data/Calculation/Statistical/CHIDISTRightTail.php
+++ b/tests/data/Calculation/Statistical/CHIDISTRightTail.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.964294972685,
diff --git a/tests/data/Calculation/Statistical/CHIINVLeftTail.php b/tests/data/Calculation/Statistical/CHIINVLeftTail.php
index bc64721e0..0be08a847 100644
--- a/tests/data/Calculation/Statistical/CHIINVLeftTail.php
+++ b/tests/data/Calculation/Statistical/CHIINVLeftTail.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         4.671330448981,
diff --git a/tests/data/Calculation/Statistical/CHIINVRightTail.php b/tests/data/Calculation/Statistical/CHIINVRightTail.php
index 58b317e59..adeb7e397 100644
--- a/tests/data/Calculation/Statistical/CHIINVRightTail.php
+++ b/tests/data/Calculation/Statistical/CHIINVRightTail.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         8.383430828608,
diff --git a/tests/data/Calculation/Statistical/CHITEST.php b/tests/data/Calculation/Statistical/CHITEST.php
index 6f5cd05c6..b32a86ea9 100644
--- a/tests/data/Calculation/Statistical/CHITEST.php
+++ b/tests/data/Calculation/Statistical/CHITEST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.0152703571482,
diff --git a/tests/data/Calculation/Statistical/CONFIDENCE.php b/tests/data/Calculation/Statistical/CONFIDENCE.php
index 8fd68abc8..f36898b4e 100644
--- a/tests/data/Calculation/Statistical/CONFIDENCE.php
+++ b/tests/data/Calculation/Statistical/CONFIDENCE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.692951912734,
diff --git a/tests/data/Calculation/Statistical/CORREL.php b/tests/data/Calculation/Statistical/CORREL.php
index 409abbd6d..2f3d139bf 100644
--- a/tests/data/Calculation/Statistical/CORREL.php
+++ b/tests/data/Calculation/Statistical/CORREL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.997054485502,
diff --git a/tests/data/Calculation/Statistical/COUNTA.php b/tests/data/Calculation/Statistical/COUNTA.php
index b6a9bd944..de27193b0 100644
--- a/tests/data/Calculation/Statistical/COUNTA.php
+++ b/tests/data/Calculation/Statistical/COUNTA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Shared\Date;
 
 return [
diff --git a/tests/data/Calculation/Statistical/COUNTBLANK.php b/tests/data/Calculation/Statistical/COUNTBLANK.php
index 35b43167e..6446a56b0 100644
--- a/tests/data/Calculation/Statistical/COUNTBLANK.php
+++ b/tests/data/Calculation/Statistical/COUNTBLANK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         4,
diff --git a/tests/data/Calculation/Statistical/COUNTIF.php b/tests/data/Calculation/Statistical/COUNTIF.php
index 0abf8ae3f..bdd7f6dfa 100644
--- a/tests/data/Calculation/Statistical/COUNTIF.php
+++ b/tests/data/Calculation/Statistical/COUNTIF.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/Statistical/COUNTIFS.php b/tests/data/Calculation/Statistical/COUNTIFS.php
index 2f7fc97fe..614d83200 100644
--- a/tests/data/Calculation/Statistical/COUNTIFS.php
+++ b/tests/data/Calculation/Statistical/COUNTIFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no argument' => [
         'exception',
diff --git a/tests/data/Calculation/Statistical/COVAR.php b/tests/data/Calculation/Statistical/COVAR.php
index d32cc8b3c..f02bbad8e 100644
--- a/tests/data/Calculation/Statistical/COVAR.php
+++ b/tests/data/Calculation/Statistical/COVAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5.2,
diff --git a/tests/data/Calculation/Statistical/DEVSQ.php b/tests/data/Calculation/Statistical/DEVSQ.php
index 8c1bae210..4b67e44ea 100644
--- a/tests/data/Calculation/Statistical/DEVSQ.php
+++ b/tests/data/Calculation/Statistical/DEVSQ.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         48,
diff --git a/tests/data/Calculation/Statistical/EXPONDIST.php b/tests/data/Calculation/Statistical/EXPONDIST.php
index fda340db1..4afc39226 100644
--- a/tests/data/Calculation/Statistical/EXPONDIST.php
+++ b/tests/data/Calculation/Statistical/EXPONDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1.353352832366,
diff --git a/tests/data/Calculation/Statistical/ExcelCOUNT.php b/tests/data/Calculation/Statistical/ExcelCOUNT.php
index 0b1c172f1..06863488a 100644
--- a/tests/data/Calculation/Statistical/ExcelCOUNT.php
+++ b/tests/data/Calculation/Statistical/ExcelCOUNT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'passing range do not count bool, null, or text numbers' => [
         3,
diff --git a/tests/data/Calculation/Statistical/FDIST.php b/tests/data/Calculation/Statistical/FDIST.php
index 39be714d9..7ef64c6cb 100644
--- a/tests/data/Calculation/Statistical/FDIST.php
+++ b/tests/data/Calculation/Statistical/FDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.001223791709,
diff --git a/tests/data/Calculation/Statistical/FISHER.php b/tests/data/Calculation/Statistical/FISHER.php
index faf6442ea..8b07eb3cd 100644
--- a/tests/data/Calculation/Statistical/FISHER.php
+++ b/tests/data/Calculation/Statistical/FISHER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         -1.472219489583,
diff --git a/tests/data/Calculation/Statistical/FISHERINV.php b/tests/data/Calculation/Statistical/FISHERINV.php
index d23472b2e..ae6334aa3 100644
--- a/tests/data/Calculation/Statistical/FISHERINV.php
+++ b/tests/data/Calculation/Statistical/FISHERINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         -0.197375320225,
diff --git a/tests/data/Calculation/Statistical/FORECAST.php b/tests/data/Calculation/Statistical/FORECAST.php
index d14ea0a06..ade2cb8c6 100644
--- a/tests/data/Calculation/Statistical/FORECAST.php
+++ b/tests/data/Calculation/Statistical/FORECAST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         10.607253086419,
diff --git a/tests/data/Calculation/Statistical/GAMMA.php b/tests/data/Calculation/Statistical/GAMMA.php
index 24b83f045..c9b6b7a70 100644
--- a/tests/data/Calculation/Statistical/GAMMA.php
+++ b/tests/data/Calculation/Statistical/GAMMA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [1.329340388179, 2.5],
     [0.267865934620, -3.75],
diff --git a/tests/data/Calculation/Statistical/GAMMADIST.php b/tests/data/Calculation/Statistical/GAMMADIST.php
index 2a1bfa14f..9946053b7 100644
--- a/tests/data/Calculation/Statistical/GAMMADIST.php
+++ b/tests/data/Calculation/Statistical/GAMMADIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.03263913041829,
diff --git a/tests/data/Calculation/Statistical/GAMMAINV.php b/tests/data/Calculation/Statistical/GAMMAINV.php
index c35c4219e..5a321a486 100644
--- a/tests/data/Calculation/Statistical/GAMMAINV.php
+++ b/tests/data/Calculation/Statistical/GAMMAINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         10.0000111914377,
diff --git a/tests/data/Calculation/Statistical/GAMMALN.php b/tests/data/Calculation/Statistical/GAMMALN.php
index 7b43eea8e..d0dc03e09 100644
--- a/tests/data/Calculation/Statistical/GAMMALN.php
+++ b/tests/data/Calculation/Statistical/GAMMALN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2.453736570842,
diff --git a/tests/data/Calculation/Statistical/GAUSS.php b/tests/data/Calculation/Statistical/GAUSS.php
index e5dbc17e9..80a1b4158 100644
--- a/tests/data/Calculation/Statistical/GAUSS.php
+++ b/tests/data/Calculation/Statistical/GAUSS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0.4772498680518, 2],
     [-0.4999997133484, -5],
diff --git a/tests/data/Calculation/Statistical/GEOMEAN.php b/tests/data/Calculation/Statistical/GEOMEAN.php
index 139934112..58337298c 100644
--- a/tests/data/Calculation/Statistical/GEOMEAN.php
+++ b/tests/data/Calculation/Statistical/GEOMEAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5.47698696965696,
diff --git a/tests/data/Calculation/Statistical/GROWTH.php b/tests/data/Calculation/Statistical/GROWTH.php
index 25596e301..cf5d4a62c 100644
--- a/tests/data/Calculation/Statistical/GROWTH.php
+++ b/tests/data/Calculation/Statistical/GROWTH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Calculation/Statistical/GnumericCOUNT.php b/tests/data/Calculation/Statistical/GnumericCOUNT.php
index bd2b03473..aadcd23e0 100644
--- a/tests/data/Calculation/Statistical/GnumericCOUNT.php
+++ b/tests/data/Calculation/Statistical/GnumericCOUNT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'range does not count bool, null, text string' => [
         3,
diff --git a/tests/data/Calculation/Statistical/HARMEAN.php b/tests/data/Calculation/Statistical/HARMEAN.php
index 1c34ff332..e8db95a6f 100644
--- a/tests/data/Calculation/Statistical/HARMEAN.php
+++ b/tests/data/Calculation/Statistical/HARMEAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5.028375962062,
diff --git a/tests/data/Calculation/Statistical/HYPGEOMDIST.php b/tests/data/Calculation/Statistical/HYPGEOMDIST.php
index aae0a05fd..a56084bd3 100644
--- a/tests/data/Calculation/Statistical/HYPGEOMDIST.php
+++ b/tests/data/Calculation/Statistical/HYPGEOMDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.3632610939112,
diff --git a/tests/data/Calculation/Statistical/INTERCEPT.php b/tests/data/Calculation/Statistical/INTERCEPT.php
index f4f25a28d..b4fc75509 100644
--- a/tests/data/Calculation/Statistical/INTERCEPT.php
+++ b/tests/data/Calculation/Statistical/INTERCEPT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         25.0,
diff --git a/tests/data/Calculation/Statistical/KURT.php b/tests/data/Calculation/Statistical/KURT.php
index bc3a009c7..8036ec09f 100644
--- a/tests/data/Calculation/Statistical/KURT.php
+++ b/tests/data/Calculation/Statistical/KURT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return[
     [
         -0.1517996372084,
diff --git a/tests/data/Calculation/Statistical/LARGE.php b/tests/data/Calculation/Statistical/LARGE.php
index 3a6adcba9..60a3dc229 100644
--- a/tests/data/Calculation/Statistical/LARGE.php
+++ b/tests/data/Calculation/Statistical/LARGE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5,
diff --git a/tests/data/Calculation/Statistical/LINEST.php b/tests/data/Calculation/Statistical/LINEST.php
index 429c6a766..ceae99db4 100644
--- a/tests/data/Calculation/Statistical/LINEST.php
+++ b/tests/data/Calculation/Statistical/LINEST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/Statistical/LOGEST.php b/tests/data/Calculation/Statistical/LOGEST.php
index bba7487b9..a15dbbf8a 100644
--- a/tests/data/Calculation/Statistical/LOGEST.php
+++ b/tests/data/Calculation/Statistical/LOGEST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [1.000174230092, 1.0],
diff --git a/tests/data/Calculation/Statistical/LOGINV.php b/tests/data/Calculation/Statistical/LOGINV.php
index 43f461553..1442caebe 100644
--- a/tests/data/Calculation/Statistical/LOGINV.php
+++ b/tests/data/Calculation/Statistical/LOGINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         4.000025209777,
diff --git a/tests/data/Calculation/Statistical/LOGNORMDIST.php b/tests/data/Calculation/Statistical/LOGNORMDIST.php
index cc1dc8712..eaf9fbe6f 100644
--- a/tests/data/Calculation/Statistical/LOGNORMDIST.php
+++ b/tests/data/Calculation/Statistical/LOGNORMDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return[
     [0.0390835557068, 4, 3.5, 1.2],
     [0.066417114799, 12, 10, 5],
diff --git a/tests/data/Calculation/Statistical/LOGNORMDIST2.php b/tests/data/Calculation/Statistical/LOGNORMDIST2.php
index 4b709f8b4..96a966b33 100644
--- a/tests/data/Calculation/Statistical/LOGNORMDIST2.php
+++ b/tests/data/Calculation/Statistical/LOGNORMDIST2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return[
     [0.0390835557068, 4, 3.5, 1.2, true],
     [0.0176175966818, 4, 3.5, 1.2, false],
diff --git a/tests/data/Calculation/Statistical/MAX.php b/tests/data/Calculation/Statistical/MAX.php
index fc1f8a0e1..b9361b6a5 100644
--- a/tests/data/Calculation/Statistical/MAX.php
+++ b/tests/data/Calculation/Statistical/MAX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27,
diff --git a/tests/data/Calculation/Statistical/MAXA.php b/tests/data/Calculation/Statistical/MAXA.php
index 992140e79..88e01e9d8 100644
--- a/tests/data/Calculation/Statistical/MAXA.php
+++ b/tests/data/Calculation/Statistical/MAXA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27,
diff --git a/tests/data/Calculation/Statistical/MAXIFS.php b/tests/data/Calculation/Statistical/MAXIFS.php
index cafdff022..a1b3fa0e4 100644
--- a/tests/data/Calculation/Statistical/MAXIFS.php
+++ b/tests/data/Calculation/Statistical/MAXIFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no argument' => [
         'exception',
diff --git a/tests/data/Calculation/Statistical/MEDIAN.php b/tests/data/Calculation/Statistical/MEDIAN.php
index bde86d480..3eca4feb8 100644
--- a/tests/data/Calculation/Statistical/MEDIAN.php
+++ b/tests/data/Calculation/Statistical/MEDIAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         8.0,
diff --git a/tests/data/Calculation/Statistical/MIN.php b/tests/data/Calculation/Statistical/MIN.php
index f53fc6e5b..3ac8898f9 100644
--- a/tests/data/Calculation/Statistical/MIN.php
+++ b/tests/data/Calculation/Statistical/MIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/Statistical/MINA.php b/tests/data/Calculation/Statistical/MINA.php
index 5722eb562..b4aa51b43 100644
--- a/tests/data/Calculation/Statistical/MINA.php
+++ b/tests/data/Calculation/Statistical/MINA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/Statistical/MINIFS.php b/tests/data/Calculation/Statistical/MINIFS.php
index 00bd56b0c..f5d11c131 100644
--- a/tests/data/Calculation/Statistical/MINIFS.php
+++ b/tests/data/Calculation/Statistical/MINIFS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no argument' => [
         'exception',
diff --git a/tests/data/Calculation/Statistical/MODE.php b/tests/data/Calculation/Statistical/MODE.php
index 7d27b33e5..a2d6eb971 100644
--- a/tests/data/Calculation/Statistical/MODE.php
+++ b/tests/data/Calculation/Statistical/MODE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [4.1, '{5.6,4.1,4.1,3,2,4.1}'], // Calculated value was #N/A
     [4.1, '5.6,4.1,4.1,3,2,4.1'],
diff --git a/tests/data/Calculation/Statistical/NEGBINOMDIST.php b/tests/data/Calculation/Statistical/NEGBINOMDIST.php
index fd983cc15..04f572c0f 100644
--- a/tests/data/Calculation/Statistical/NEGBINOMDIST.php
+++ b/tests/data/Calculation/Statistical/NEGBINOMDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.05504866037517786,
diff --git a/tests/data/Calculation/Statistical/NORMDIST.php b/tests/data/Calculation/Statistical/NORMDIST.php
index 7ff3f8d8d..60203b484 100644
--- a/tests/data/Calculation/Statistical/NORMDIST.php
+++ b/tests/data/Calculation/Statistical/NORMDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0.9087887802741, 42, 40, 1.5, true],
     [0.109340049784, 42, 40, 1.5, false],
diff --git a/tests/data/Calculation/Statistical/NORMINV.php b/tests/data/Calculation/Statistical/NORMINV.php
index db4bac2bd..9acd94d21 100644
--- a/tests/data/Calculation/Statistical/NORMINV.php
+++ b/tests/data/Calculation/Statistical/NORMINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [42.000002008416, 0.908789, 40, 1.5],
     [5.50669420572, 0.6, 5, 2],
diff --git a/tests/data/Calculation/Statistical/NORMSDIST.php b/tests/data/Calculation/Statistical/NORMSDIST.php
index aeb540597..da94962cb 100644
--- a/tests/data/Calculation/Statistical/NORMSDIST.php
+++ b/tests/data/Calculation/Statistical/NORMSDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0.908788780274, 1.333333333333],
     [0.788144601416, 0.8],
diff --git a/tests/data/Calculation/Statistical/NORMSDIST2.php b/tests/data/Calculation/Statistical/NORMSDIST2.php
index 0f7c06d86..27accdc15 100644
--- a/tests/data/Calculation/Statistical/NORMSDIST2.php
+++ b/tests/data/Calculation/Statistical/NORMSDIST2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [0.908788780274, 1.333333333333, true],
     [0.164010074676, 1.333333333333, false],
diff --git a/tests/data/Calculation/Statistical/NORMSINV.php b/tests/data/Calculation/Statistical/NORMSINV.php
index 206bd1633..739003a42 100644
--- a/tests/data/Calculation/Statistical/NORMSINV.php
+++ b/tests/data/Calculation/Statistical/NORMSINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [1.33333467227723, 0.908789],
     [-0.67448975022342, 0.25],
diff --git a/tests/data/Calculation/Statistical/OpenOfficeCOUNT.php b/tests/data/Calculation/Statistical/OpenOfficeCOUNT.php
index 726e12a5b..82faafb24 100644
--- a/tests/data/Calculation/Statistical/OpenOfficeCOUNT.php
+++ b/tests/data/Calculation/Statistical/OpenOfficeCOUNT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'passing range count bool but not null nor text numbers' => [
         5,
diff --git a/tests/data/Calculation/Statistical/PERCENTILE.php b/tests/data/Calculation/Statistical/PERCENTILE.php
index 890399c53..4cf5173b6 100644
--- a/tests/data/Calculation/Statistical/PERCENTILE.php
+++ b/tests/data/Calculation/Statistical/PERCENTILE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1.9,
diff --git a/tests/data/Calculation/Statistical/PERCENTRANK.php b/tests/data/Calculation/Statistical/PERCENTRANK.php
index 3787a7ac1..fc8840f7a 100644
--- a/tests/data/Calculation/Statistical/PERCENTRANK.php
+++ b/tests/data/Calculation/Statistical/PERCENTRANK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.667,
diff --git a/tests/data/Calculation/Statistical/PERMUT.php b/tests/data/Calculation/Statistical/PERMUT.php
index 80b3a93de..50fe816f7 100644
--- a/tests/data/Calculation/Statistical/PERMUT.php
+++ b/tests/data/Calculation/Statistical/PERMUT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5,
diff --git a/tests/data/Calculation/Statistical/PERMUTATIONA.php b/tests/data/Calculation/Statistical/PERMUTATIONA.php
index 701f5eac4..fdaee63af 100644
--- a/tests/data/Calculation/Statistical/PERMUTATIONA.php
+++ b/tests/data/Calculation/Statistical/PERMUTATIONA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         5,
diff --git a/tests/data/Calculation/Statistical/POISSON.php b/tests/data/Calculation/Statistical/POISSON.php
index 7c839ac76..4ec9474db 100644
--- a/tests/data/Calculation/Statistical/POISSON.php
+++ b/tests/data/Calculation/Statistical/POISSON.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.12465201948308113,
diff --git a/tests/data/Calculation/Statistical/QUARTILE.php b/tests/data/Calculation/Statistical/QUARTILE.php
index 33f0ea8b8..70810fd8c 100644
--- a/tests/data/Calculation/Statistical/QUARTILE.php
+++ b/tests/data/Calculation/Statistical/QUARTILE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3.5,
diff --git a/tests/data/Calculation/Statistical/RANK.php b/tests/data/Calculation/Statistical/RANK.php
index 0ca23581d..ccd7ca219 100644
--- a/tests/data/Calculation/Statistical/RANK.php
+++ b/tests/data/Calculation/Statistical/RANK.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         2,
diff --git a/tests/data/Calculation/Statistical/RSQ.php b/tests/data/Calculation/Statistical/RSQ.php
index f414ef555..3565f58a5 100644
--- a/tests/data/Calculation/Statistical/RSQ.php
+++ b/tests/data/Calculation/Statistical/RSQ.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.057950191571,
diff --git a/tests/data/Calculation/Statistical/SKEW.php b/tests/data/Calculation/Statistical/SKEW.php
index 9384613f2..afbb1ee83 100644
--- a/tests/data/Calculation/Statistical/SKEW.php
+++ b/tests/data/Calculation/Statistical/SKEW.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.359543071407,
diff --git a/tests/data/Calculation/Statistical/SLOPE.php b/tests/data/Calculation/Statistical/SLOPE.php
index a7730b9cd..c8d4a827b 100644
--- a/tests/data/Calculation/Statistical/SLOPE.php
+++ b/tests/data/Calculation/Statistical/SLOPE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Shared\Date;
 
 return [
diff --git a/tests/data/Calculation/Statistical/SMALL.php b/tests/data/Calculation/Statistical/SMALL.php
index d33956602..7efaf8a9b 100644
--- a/tests/data/Calculation/Statistical/SMALL.php
+++ b/tests/data/Calculation/Statistical/SMALL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3,
diff --git a/tests/data/Calculation/Statistical/STANDARDIZE.php b/tests/data/Calculation/Statistical/STANDARDIZE.php
index c2e4c9f78..605f07099 100644
--- a/tests/data/Calculation/Statistical/STANDARDIZE.php
+++ b/tests/data/Calculation/Statistical/STANDARDIZE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [1.333333333333, 42, 40, 1.5],
     [0.25, 5.5, 5, 2],
diff --git a/tests/data/Calculation/Statistical/STDEV.php b/tests/data/Calculation/Statistical/STDEV.php
index 30d9dc3b8..03a301813 100644
--- a/tests/data/Calculation/Statistical/STDEV.php
+++ b/tests/data/Calculation/Statistical/STDEV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27.463915719843,
diff --git a/tests/data/Calculation/Statistical/STDEVA.php b/tests/data/Calculation/Statistical/STDEVA.php
index 13cecc617..cc3b88808 100644
--- a/tests/data/Calculation/Statistical/STDEVA.php
+++ b/tests/data/Calculation/Statistical/STDEVA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27.463915719843,
diff --git a/tests/data/Calculation/Statistical/STDEVA_ODS.php b/tests/data/Calculation/Statistical/STDEVA_ODS.php
index 559798e46..f0fe11b31 100644
--- a/tests/data/Calculation/Statistical/STDEVA_ODS.php
+++ b/tests/data/Calculation/Statistical/STDEVA_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27.463915719843,
diff --git a/tests/data/Calculation/Statistical/STDEVP.php b/tests/data/Calculation/Statistical/STDEVP.php
index 443a993c1..964dc3d8d 100644
--- a/tests/data/Calculation/Statistical/STDEVP.php
+++ b/tests/data/Calculation/Statistical/STDEVP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         26.0545581424825,
diff --git a/tests/data/Calculation/Statistical/STDEVPA.php b/tests/data/Calculation/Statistical/STDEVPA.php
index 3ca865a3d..536763ae4 100644
--- a/tests/data/Calculation/Statistical/STDEVPA.php
+++ b/tests/data/Calculation/Statistical/STDEVPA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         26.0545581424825,
diff --git a/tests/data/Calculation/Statistical/STDEVPA_ODS.php b/tests/data/Calculation/Statistical/STDEVPA_ODS.php
index 3ca865a3d..536763ae4 100644
--- a/tests/data/Calculation/Statistical/STDEVPA_ODS.php
+++ b/tests/data/Calculation/Statistical/STDEVPA_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         26.0545581424825,
diff --git a/tests/data/Calculation/Statistical/STDEVP_ODS.php b/tests/data/Calculation/Statistical/STDEVP_ODS.php
index 131a23977..e672b2986 100644
--- a/tests/data/Calculation/Statistical/STDEVP_ODS.php
+++ b/tests/data/Calculation/Statistical/STDEVP_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         26.0545581424825,
diff --git a/tests/data/Calculation/Statistical/STDEV_ODS.php b/tests/data/Calculation/Statistical/STDEV_ODS.php
index 7129ed0b7..481f4f6d4 100644
--- a/tests/data/Calculation/Statistical/STDEV_ODS.php
+++ b/tests/data/Calculation/Statistical/STDEV_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         27.463915719843,
diff --git a/tests/data/Calculation/Statistical/STEYX.php b/tests/data/Calculation/Statistical/STEYX.php
index a87ff5922..80c6587c6 100644
--- a/tests/data/Calculation/Statistical/STEYX.php
+++ b/tests/data/Calculation/Statistical/STEYX.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3.305718950210,
diff --git a/tests/data/Calculation/Statistical/TDIST.php b/tests/data/Calculation/Statistical/TDIST.php
index 7bf046fc4..298675a45 100644
--- a/tests/data/Calculation/Statistical/TDIST.php
+++ b/tests/data/Calculation/Statistical/TDIST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.027322464988,
diff --git a/tests/data/Calculation/Statistical/TINV.php b/tests/data/Calculation/Statistical/TINV.php
index e288bcd06..ec602c7fc 100644
--- a/tests/data/Calculation/Statistical/TINV.php
+++ b/tests/data/Calculation/Statistical/TINV.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1.960041187127,
diff --git a/tests/data/Calculation/Statistical/TREND.php b/tests/data/Calculation/Statistical/TREND.php
index 418367b2e..adac7afe6 100644
--- a/tests/data/Calculation/Statistical/TREND.php
+++ b/tests/data/Calculation/Statistical/TREND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Calculation/Statistical/TRIMMEAN.php b/tests/data/Calculation/Statistical/TRIMMEAN.php
index 5ec07a04f..a009e078d 100644
--- a/tests/data/Calculation/Statistical/TRIMMEAN.php
+++ b/tests/data/Calculation/Statistical/TRIMMEAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3.777777777778,
diff --git a/tests/data/Calculation/Statistical/VAR.php b/tests/data/Calculation/Statistical/VAR.php
index baedd48cd..92ab96e60 100644
--- a/tests/data/Calculation/Statistical/VAR.php
+++ b/tests/data/Calculation/Statistical/VAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         754.266666666667,
diff --git a/tests/data/Calculation/Statistical/VARA.php b/tests/data/Calculation/Statistical/VARA.php
index 444a789ea..5dd68c774 100644
--- a/tests/data/Calculation/Statistical/VARA.php
+++ b/tests/data/Calculation/Statistical/VARA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         754.266666666667,
diff --git a/tests/data/Calculation/Statistical/VARA_ODS.php b/tests/data/Calculation/Statistical/VARA_ODS.php
index 444a789ea..5dd68c774 100644
--- a/tests/data/Calculation/Statistical/VARA_ODS.php
+++ b/tests/data/Calculation/Statistical/VARA_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         754.266666666667,
diff --git a/tests/data/Calculation/Statistical/VARP.php b/tests/data/Calculation/Statistical/VARP.php
index 519de42bf..9845125d7 100644
--- a/tests/data/Calculation/Statistical/VARP.php
+++ b/tests/data/Calculation/Statistical/VARP.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         678.84,
diff --git a/tests/data/Calculation/Statistical/VARPA.php b/tests/data/Calculation/Statistical/VARPA.php
index a78a01793..52a1d4936 100644
--- a/tests/data/Calculation/Statistical/VARPA.php
+++ b/tests/data/Calculation/Statistical/VARPA.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         678.84,
diff --git a/tests/data/Calculation/Statistical/VARPA_ODS.php b/tests/data/Calculation/Statistical/VARPA_ODS.php
index a78a01793..52a1d4936 100644
--- a/tests/data/Calculation/Statistical/VARPA_ODS.php
+++ b/tests/data/Calculation/Statistical/VARPA_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         678.84,
diff --git a/tests/data/Calculation/Statistical/VARP_ODS.php b/tests/data/Calculation/Statistical/VARP_ODS.php
index a78a01793..52a1d4936 100644
--- a/tests/data/Calculation/Statistical/VARP_ODS.php
+++ b/tests/data/Calculation/Statistical/VARP_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         678.84,
diff --git a/tests/data/Calculation/Statistical/VAR_ODS.php b/tests/data/Calculation/Statistical/VAR_ODS.php
index 444a789ea..5dd68c774 100644
--- a/tests/data/Calculation/Statistical/VAR_ODS.php
+++ b/tests/data/Calculation/Statistical/VAR_ODS.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         754.266666666667,
diff --git a/tests/data/Calculation/Statistical/WEIBULL.php b/tests/data/Calculation/Statistical/WEIBULL.php
index 87f47ad28..002f26032 100644
--- a/tests/data/Calculation/Statistical/WEIBULL.php
+++ b/tests/data/Calculation/Statistical/WEIBULL.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.929581390070,
diff --git a/tests/data/Calculation/Statistical/ZTEST.php b/tests/data/Calculation/Statistical/ZTEST.php
index 9de2a8370..235048d11 100644
--- a/tests/data/Calculation/Statistical/ZTEST.php
+++ b/tests/data/Calculation/Statistical/ZTEST.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0.090574196851,
diff --git a/tests/data/Calculation/TextData/ARRAYTOTEXT.php b/tests/data/Calculation/TextData/ARRAYTOTEXT.php
index 4bef2823d..f5dd6cb14 100644
--- a/tests/data/Calculation/TextData/ARRAYTOTEXT.php
+++ b/tests/data/Calculation/TextData/ARRAYTOTEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         "1, 2, 3, a, b, c, TRUE, FALSE, #DIV/0!, 44774, 1, 44777, 12345.6789, -2.4, Hello\nWorld",
diff --git a/tests/data/Calculation/TextData/CHAR.php b/tests/data/Calculation/TextData/CHAR.php
index f02437b7d..400edd50d 100644
--- a/tests/data/Calculation/TextData/CHAR.php
+++ b/tests/data/Calculation/TextData/CHAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#VALUE!',
diff --git a/tests/data/Calculation/TextData/CLEAN.php b/tests/data/Calculation/TextData/CLEAN.php
index ad668271a..255a8222f 100644
--- a/tests/data/Calculation/TextData/CLEAN.php
+++ b/tests/data/Calculation/TextData/CLEAN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'HELLO      ',
diff --git a/tests/data/Calculation/TextData/CODE.php b/tests/data/Calculation/TextData/CODE.php
index 8ab927263..62bd213b2 100644
--- a/tests/data/Calculation/TextData/CODE.php
+++ b/tests/data/Calculation/TextData/CODE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#VALUE!',
diff --git a/tests/data/Calculation/TextData/CONCATENATE.php b/tests/data/Calculation/TextData/CONCATENATE.php
index b29843f7f..c37c2ffcd 100644
--- a/tests/data/Calculation/TextData/CONCATENATE.php
+++ b/tests/data/Calculation/TextData/CONCATENATE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
 
 return [
diff --git a/tests/data/Calculation/TextData/DOLLAR.php b/tests/data/Calculation/TextData/DOLLAR.php
index 78fcc1b52..d20e173d1 100644
--- a/tests/data/Calculation/TextData/DOLLAR.php
+++ b/tests/data/Calculation/TextData/DOLLAR.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '$123.46',
diff --git a/tests/data/Calculation/TextData/EXACT.php b/tests/data/Calculation/TextData/EXACT.php
index f392b0b05..aa54f6f2f 100644
--- a/tests/data/Calculation/TextData/EXACT.php
+++ b/tests/data/Calculation/TextData/EXACT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         true,
diff --git a/tests/data/Calculation/TextData/FIND.php b/tests/data/Calculation/TextData/FIND.php
index 1ae6d730e..027f62d2d 100644
--- a/tests/data/Calculation/TextData/FIND.php
+++ b/tests/data/Calculation/TextData/FIND.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3,
diff --git a/tests/data/Calculation/TextData/FIXED.php b/tests/data/Calculation/TextData/FIXED.php
index 29734404c..e13b8110e 100644
--- a/tests/data/Calculation/TextData/FIXED.php
+++ b/tests/data/Calculation/TextData/FIXED.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '123,456.79',
diff --git a/tests/data/Calculation/TextData/LEFT.php b/tests/data/Calculation/TextData/LEFT.php
index 17d3fcf7a..1bf71c99d 100644
--- a/tests/data/Calculation/TextData/LEFT.php
+++ b/tests/data/Calculation/TextData/LEFT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '',
diff --git a/tests/data/Calculation/TextData/LEN.php b/tests/data/Calculation/TextData/LEN.php
index babf3535a..e07be820c 100644
--- a/tests/data/Calculation/TextData/LEN.php
+++ b/tests/data/Calculation/TextData/LEN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         0,
diff --git a/tests/data/Calculation/TextData/LOWER.php b/tests/data/Calculation/TextData/LOWER.php
index 23825546d..39c286f8b 100644
--- a/tests/data/Calculation/TextData/LOWER.php
+++ b/tests/data/Calculation/TextData/LOWER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'abcdefghi',
diff --git a/tests/data/Calculation/TextData/MID.php b/tests/data/Calculation/TextData/MID.php
index 45e0ceab9..9379b9471 100644
--- a/tests/data/Calculation/TextData/MID.php
+++ b/tests/data/Calculation/TextData/MID.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '',
diff --git a/tests/data/Calculation/TextData/NUMBERVALUE.php b/tests/data/Calculation/TextData/NUMBERVALUE.php
index 613131742..5e979763f 100644
--- a/tests/data/Calculation/TextData/NUMBERVALUE.php
+++ b/tests/data/Calculation/TextData/NUMBERVALUE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1234567.89,
diff --git a/tests/data/Calculation/TextData/OpenOffice.php b/tests/data/Calculation/TextData/OpenOffice.php
index fc79d5f11..5c1c4a035 100644
--- a/tests/data/Calculation/TextData/OpenOffice.php
+++ b/tests/data/Calculation/TextData/OpenOffice.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'OO allows CHAR(0)' => ["\x00", '=CHAR(0)'],
     'OO treats CODE(bool) as 0/1' => ['48', '=CODE(FALSE)'],
diff --git a/tests/data/Calculation/TextData/PROPER.php b/tests/data/Calculation/TextData/PROPER.php
index e9a5d4ceb..6798151c0 100644
--- a/tests/data/Calculation/TextData/PROPER.php
+++ b/tests/data/Calculation/TextData/PROPER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'Mark Baker',
diff --git a/tests/data/Calculation/TextData/REPLACE.php b/tests/data/Calculation/TextData/REPLACE.php
index 2268bf48d..d36e7beb6 100644
--- a/tests/data/Calculation/TextData/REPLACE.php
+++ b/tests/data/Calculation/TextData/REPLACE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'QWDFGYUIOP',
diff --git a/tests/data/Calculation/TextData/REPT.php b/tests/data/Calculation/TextData/REPT.php
index 172d8faee..f3369c506 100644
--- a/tests/data/Calculation/TextData/REPT.php
+++ b/tests/data/Calculation/TextData/REPT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'no arguments' => ['exception'],
     'one argument' => ['exception', 'ABC'],
diff --git a/tests/data/Calculation/TextData/RIGHT.php b/tests/data/Calculation/TextData/RIGHT.php
index 77ea64bf7..922a3591e 100644
--- a/tests/data/Calculation/TextData/RIGHT.php
+++ b/tests/data/Calculation/TextData/RIGHT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '',
diff --git a/tests/data/Calculation/TextData/SEARCH.php b/tests/data/Calculation/TextData/SEARCH.php
index 335a7f12a..34600d309 100644
--- a/tests/data/Calculation/TextData/SEARCH.php
+++ b/tests/data/Calculation/TextData/SEARCH.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3,
diff --git a/tests/data/Calculation/TextData/SUBSTITUTE.php b/tests/data/Calculation/TextData/SUBSTITUTE.php
index baf1c87b2..8d9b90a0a 100644
--- a/tests/data/Calculation/TextData/SUBSTITUTE.php
+++ b/tests/data/Calculation/TextData/SUBSTITUTE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'QWDFGYUIOP',
diff --git a/tests/data/Calculation/TextData/T.php b/tests/data/Calculation/TextData/T.php
index 802b936fa..7fab8a1e9 100644
--- a/tests/data/Calculation/TextData/T.php
+++ b/tests/data/Calculation/TextData/T.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '',
diff --git a/tests/data/Calculation/TextData/TEXT.php b/tests/data/Calculation/TextData/TEXT.php
index 5bf87a87d..19032d006 100644
--- a/tests/data/Calculation/TextData/TEXT.php
+++ b/tests/data/Calculation/TextData/TEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '$123.46',
diff --git a/tests/data/Calculation/TextData/TEXTAFTER.php b/tests/data/Calculation/TextData/TEXTAFTER.php
index c0e3e3d51..ba22ce55d 100644
--- a/tests/data/Calculation/TextData/TEXTAFTER.php
+++ b/tests/data/Calculation/TextData/TEXTAFTER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/TextData/TEXTBEFORE.php b/tests/data/Calculation/TextData/TEXTBEFORE.php
index a79d37b0f..7987908da 100644
--- a/tests/data/Calculation/TextData/TEXTBEFORE.php
+++ b/tests/data/Calculation/TextData/TEXTBEFORE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/TextData/TEXTJOIN.php b/tests/data/Calculation/TextData/TEXTJOIN.php
index 392f7e4f2..3908abb87 100644
--- a/tests/data/Calculation/TextData/TEXTJOIN.php
+++ b/tests/data/Calculation/TextData/TEXTJOIN.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
 
 return [
diff --git a/tests/data/Calculation/TextData/TEXTSPLIT.php b/tests/data/Calculation/TextData/TEXTSPLIT.php
index a10b26f6e..118685a70 100644
--- a/tests/data/Calculation/TextData/TEXTSPLIT.php
+++ b/tests/data/Calculation/TextData/TEXTSPLIT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 
 return [
diff --git a/tests/data/Calculation/TextData/TRIM.php b/tests/data/Calculation/TextData/TRIM.php
index 882dc824d..42c3b3965 100644
--- a/tests/data/Calculation/TextData/TRIM.php
+++ b/tests/data/Calculation/TextData/TRIM.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'HELLO',
diff --git a/tests/data/Calculation/TextData/UPPER.php b/tests/data/Calculation/TextData/UPPER.php
index 21b04ae46..5810fbe32 100644
--- a/tests/data/Calculation/TextData/UPPER.php
+++ b/tests/data/Calculation/TextData/UPPER.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'ABCDEFGHI',
diff --git a/tests/data/Calculation/TextData/VALUE.php b/tests/data/Calculation/TextData/VALUE.php
index 1a007005e..c55888107 100644
--- a/tests/data/Calculation/TextData/VALUE.php
+++ b/tests/data/Calculation/TextData/VALUE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '1000',
diff --git a/tests/data/Calculation/TextData/VALUETOTEXT.php b/tests/data/Calculation/TextData/VALUETOTEXT.php
index 13df19ab1..b3871a43a 100644
--- a/tests/data/Calculation/TextData/VALUETOTEXT.php
+++ b/tests/data/Calculation/TextData/VALUETOTEXT.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
 
 $richText1 = new RichText();
diff --git a/tests/data/Calculation/Translations.php b/tests/data/Calculation/Translations.php
index 0965bac1c..b0849ff27 100644
--- a/tests/data/Calculation/Translations.php
+++ b/tests/data/Calculation/Translations.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '=DAGEN360(DATUM(2010;2;5);DATUM(2010;12;31);WAAR)',
diff --git a/tests/data/Calculation/Web/URLENCODE.php b/tests/data/Calculation/Web/URLENCODE.php
index 3a227ae5c..fcc9dc034 100644
--- a/tests/data/Calculation/Web/URLENCODE.php
+++ b/tests/data/Calculation/Web/URLENCODE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'http%3A%2F%2Fcontoso.sharepoint.com%2Fteams%2FFinance%2FDocuments%2FApril%20Reports%2FProfit%20and%20Loss%20Statement.xlsx',
diff --git a/tests/data/Calculation/Web/WEBSERVICE.php b/tests/data/Calculation/Web/WEBSERVICE.php
index 418761411..f2c6f9008 100644
--- a/tests/data/Calculation/Web/WEBSERVICE.php
+++ b/tests/data/Calculation/Web/WEBSERVICE.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '#VALUE!',
diff --git a/tests/data/CalculationBinaryComparisonOperation.php b/tests/data/CalculationBinaryComparisonOperation.php
index a8c8e4ece..2826b9b75 100644
--- a/tests/data/CalculationBinaryComparisonOperation.php
+++ b/tests/data/CalculationBinaryComparisonOperation.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 //  formula, expectedResultExcel, expectedResultOpenOffice
 
 return [
diff --git a/tests/data/Cell/A1ConversionToR1C1Absolute.php b/tests/data/Cell/A1ConversionToR1C1Absolute.php
index 171672bbf..14e6ec611 100644
--- a/tests/data/Cell/A1ConversionToR1C1Absolute.php
+++ b/tests/data/Cell/A1ConversionToR1C1Absolute.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['R1C1', 'A1'],
     ['R1C1', '$A$1'],
diff --git a/tests/data/Cell/A1ConversionToR1C1Exception.php b/tests/data/Cell/A1ConversionToR1C1Exception.php
index 7dd4a68ed..f8b0ee9bb 100644
--- a/tests/data/Cell/A1ConversionToR1C1Exception.php
+++ b/tests/data/Cell/A1ConversionToR1C1Exception.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['A11Y'],
 ];
diff --git a/tests/data/Cell/A1ConversionToR1C1Relative.php b/tests/data/Cell/A1ConversionToR1C1Relative.php
index dd9b23918..8824c4916 100644
--- a/tests/data/Cell/A1ConversionToR1C1Relative.php
+++ b/tests/data/Cell/A1ConversionToR1C1Relative.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['R[2]C[2]', 'O18', 16, 13],
     ['R18C15', '$O$18', 16, 13],
diff --git a/tests/data/Cell/ConvertFormulaToA1FromR1C1Absolute.php b/tests/data/Cell/ConvertFormulaToA1FromR1C1Absolute.php
index 5624c0c96..d4d0f2854 100644
--- a/tests/data/Cell/ConvertFormulaToA1FromR1C1Absolute.php
+++ b/tests/data/Cell/ConvertFormulaToA1FromR1C1Absolute.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'Basic addition' => ['=D3+F7+G4+C6+5', '=R3C4+R7C6+R4C7+R6C3+5'],
     'Basic subtraction' => ['=D3-F7-G4-C6-5', '=R3C4-R7C6-R4C7-R6C3-5'],
diff --git a/tests/data/Cell/ConvertFormulaToA1FromR1C1Relative.php b/tests/data/Cell/ConvertFormulaToA1FromR1C1Relative.php
index d6df418cd..84e11af3b 100644
--- a/tests/data/Cell/ConvertFormulaToA1FromR1C1Relative.php
+++ b/tests/data/Cell/ConvertFormulaToA1FromR1C1Relative.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'Basic addition' => ['=D3+F7+G4+C6+5', '=R[-2]C[-1]+R[2]C[1]+R[-1]C[2]+R[1]C[-2]+5', 5, 5],
     'Basic subtraction' => ['=D3-F7-G4-C6-5', '=R[-2]C[-1]-R[2]C[1]-R[-1]C[2]-R[1]C[-2]-5', 5, 5],
diff --git a/tests/data/Cell/ConvertFormulaToA1FromSpreadsheetXml.php b/tests/data/Cell/ConvertFormulaToA1FromSpreadsheetXml.php
index d350c07b3..915d1a468 100644
--- a/tests/data/Cell/ConvertFormulaToA1FromSpreadsheetXml.php
+++ b/tests/data/Cell/ConvertFormulaToA1FromSpreadsheetXml.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'Basic addition' => ['=D3+F7+G4+C6+5', 'of:=[.D3]+[.F7]+[.G4]+[.C6]+5'],
     'Basic subtraction' => ['=D3-F7-G4-C6-5', 'of:=[.D3]-[.F7]-[.G4]-[.C6]-5'],
diff --git a/tests/data/Cell/DefaultValueBinder.php b/tests/data/Cell/DefaultValueBinder.php
index f5dafc7bc..b9f3d51e1 100644
--- a/tests/data/Cell/DefaultValueBinder.php
+++ b/tests/data/Cell/DefaultValueBinder.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'null',
diff --git a/tests/data/Cell/IndexesFromString.php b/tests/data/Cell/IndexesFromString.php
index 0a79e47f4..4b223a5a3 100644
--- a/tests/data/Cell/IndexesFromString.php
+++ b/tests/data/Cell/IndexesFromString.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/Cell/R1C1ConversionToA1Absolute.php b/tests/data/Cell/R1C1ConversionToA1Absolute.php
index 8828934ea..ff619b797 100644
--- a/tests/data/Cell/R1C1ConversionToA1Absolute.php
+++ b/tests/data/Cell/R1C1ConversionToA1Absolute.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['A1', 'R1C1'],
     ['B2', 'R2C2'],
diff --git a/tests/data/Cell/R1C1ConversionToA1Exception.php b/tests/data/Cell/R1C1ConversionToA1Exception.php
index fa27fbe95..eb3aa8367 100644
--- a/tests/data/Cell/R1C1ConversionToA1Exception.php
+++ b/tests/data/Cell/R1C1ConversionToA1Exception.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['RICE'],
     ['R[-1]C'],
diff --git a/tests/data/Cell/R1C1ConversionToA1Relative.php b/tests/data/Cell/R1C1ConversionToA1Relative.php
index 9e7d97ba3..5a74970cb 100644
--- a/tests/data/Cell/R1C1ConversionToA1Relative.php
+++ b/tests/data/Cell/R1C1ConversionToA1Relative.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     ['C3', 'R[2]C[2]'],
     ['O18', 'R[2]C[2]', 16, 13],
diff --git a/tests/data/Cell/SetValueExplicit.php b/tests/data/Cell/SetValueExplicit.php
index 13a1e33a5..2bb7b01b4 100644
--- a/tests/data/Cell/SetValueExplicit.php
+++ b/tests/data/Cell/SetValueExplicit.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
 
diff --git a/tests/data/Cell/SetValueExplicitException.php b/tests/data/Cell/SetValueExplicitException.php
index a05704f02..6b1508190 100644
--- a/tests/data/Cell/SetValueExplicitException.php
+++ b/tests/data/Cell/SetValueExplicitException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Cell\DataType;
 
 return [
diff --git a/tests/data/CellAbsoluteCoordinate.php b/tests/data/CellAbsoluteCoordinate.php
index 86487585c..a8e304125 100644
--- a/tests/data/CellAbsoluteCoordinate.php
+++ b/tests/data/CellAbsoluteCoordinate.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '$A$1',
diff --git a/tests/data/CellAbsoluteReference.php b/tests/data/CellAbsoluteReference.php
index 71dac5454..d628d800f 100644
--- a/tests/data/CellAbsoluteReference.php
+++ b/tests/data/CellAbsoluteReference.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '$A$1',
diff --git a/tests/data/CellBuildRange.php b/tests/data/CellBuildRange.php
index 1eb0ef345..60496a5d6 100644
--- a/tests/data/CellBuildRange.php
+++ b/tests/data/CellBuildRange.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'B4:E9',
diff --git a/tests/data/CellCoordinates.php b/tests/data/CellCoordinates.php
index 694856ccb..78f841ef0 100644
--- a/tests/data/CellCoordinates.php
+++ b/tests/data/CellCoordinates.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/CellExtractAllCellReferencesInRange.php b/tests/data/CellExtractAllCellReferencesInRange.php
index 192500ce4..02ec9f855 100644
--- a/tests/data/CellExtractAllCellReferencesInRange.php
+++ b/tests/data/CellExtractAllCellReferencesInRange.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/CellGetRangeBoundaries.php b/tests/data/CellGetRangeBoundaries.php
index 7a56b4c03..1cce2f35d 100644
--- a/tests/data/CellGetRangeBoundaries.php
+++ b/tests/data/CellGetRangeBoundaries.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'Cell Range' => [
diff --git a/tests/data/CellMergeRangesInCollection.php b/tests/data/CellMergeRangesInCollection.php
index 0a7723ee0..3be59edc3 100644
--- a/tests/data/CellMergeRangesInCollection.php
+++ b/tests/data/CellMergeRangesInCollection.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/CellRangeBoundaries.php b/tests/data/CellRangeBoundaries.php
index 882f437cd..d3804ebae 100644
--- a/tests/data/CellRangeBoundaries.php
+++ b/tests/data/CellRangeBoundaries.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'Cell Range' => [
         [
diff --git a/tests/data/CellRangeDimension.php b/tests/data/CellRangeDimension.php
index a3e15531c..ca289179b 100644
--- a/tests/data/CellRangeDimension.php
+++ b/tests/data/CellRangeDimension.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/CellSplitRange.php b/tests/data/CellSplitRange.php
index a7d701c3f..ba2ab37ea 100644
--- a/tests/data/CellSplitRange.php
+++ b/tests/data/CellSplitRange.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         [
diff --git a/tests/data/ColumnIndex.php b/tests/data/ColumnIndex.php
index 750ef823f..0bb2bdc99 100644
--- a/tests/data/ColumnIndex.php
+++ b/tests/data/ColumnIndex.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'A',
diff --git a/tests/data/ColumnString.php b/tests/data/ColumnString.php
index 78d21aaa7..1aaafe829 100644
--- a/tests/data/ColumnString.php
+++ b/tests/data/ColumnString.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         1,
diff --git a/tests/data/CoordinateIsRange.php b/tests/data/CoordinateIsRange.php
index 4718bdce6..a0c44089f 100644
--- a/tests/data/CoordinateIsRange.php
+++ b/tests/data/CoordinateIsRange.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         false,
diff --git a/tests/data/Functional/TypeAttributePreservation/Formula.php b/tests/data/Functional/TypeAttributePreservation/Formula.php
index c10e2a61b..6f260da47 100644
--- a/tests/data/Functional/TypeAttributePreservation/Formula.php
+++ b/tests/data/Functional/TypeAttributePreservation/Formula.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         ['string'],
diff --git a/tests/data/ReferenceHelperFormulaUpdates.php b/tests/data/ReferenceHelperFormulaUpdates.php
index ef563f31c..4dad6bf07 100644
--- a/tests/data/ReferenceHelperFormulaUpdates.php
+++ b/tests/data/ReferenceHelperFormulaUpdates.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '=IF(A$1=0,0,A1/A$1)',
diff --git a/tests/data/ReferenceHelperFormulaUpdatesMultipleSheet.php b/tests/data/ReferenceHelperFormulaUpdatesMultipleSheet.php
index 9c59359d1..f4f97e5fb 100644
--- a/tests/data/ReferenceHelperFormulaUpdatesMultipleSheet.php
+++ b/tests/data/ReferenceHelperFormulaUpdatesMultipleSheet.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         "=IF('2020'!\$B1=\"\",\"-\",(('2020'!\$B1/'2019'!\$B1)-1))",
diff --git a/tests/data/Shared/CentimeterSizeToPixels.php b/tests/data/Shared/CentimeterSizeToPixels.php
index 6ef11d938..ff519ba9d 100644
--- a/tests/data/Shared/CentimeterSizeToPixels.php
+++ b/tests/data/Shared/CentimeterSizeToPixels.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         3.7795275590999999,
diff --git a/tests/data/Shared/CodePage.php b/tests/data/Shared/CodePage.php
index ccb59f240..eca9879f6 100644
--- a/tests/data/Shared/CodePage.php
+++ b/tests/data/Shared/CodePage.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     // ANSI Latin I (BIFF4-BIFF7)
     [
diff --git a/tests/data/Shared/Date/DateTimeToExcel.php b/tests/data/Shared/Date/DateTimeToExcel.php
index a2f537af3..f5f754a75 100644
--- a/tests/data/Shared/Date/DateTimeToExcel.php
+++ b/tests/data/Shared/Date/DateTimeToExcel.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // DateTime object                          Result           Comments
 return [
     // Excel 1900 base calendar date
diff --git a/tests/data/Shared/Date/ExcelToTimestamp1900.php b/tests/data/Shared/Date/ExcelToTimestamp1900.php
index ffcd194f4..3c94a41ab 100644
--- a/tests/data/Shared/Date/ExcelToTimestamp1900.php
+++ b/tests/data/Shared/Date/ExcelToTimestamp1900.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Excel DateTimeStamp  Result            Comments
 return [
     // PHP 32-bit Earliest Date 14-Dec-1901
diff --git a/tests/data/Shared/Date/ExcelToTimestamp1900Timezone.php b/tests/data/Shared/Date/ExcelToTimestamp1900Timezone.php
index 0678723d9..3eb7be2ae 100644
--- a/tests/data/Shared/Date/ExcelToTimestamp1900Timezone.php
+++ b/tests/data/Shared/Date/ExcelToTimestamp1900Timezone.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Excel DateTimeStamp  Timezone               Result            Comments
 return [
     // 19-Dec-1960 00:00:00 EST => 19-Dec-1960 05:00:00 UTC
diff --git a/tests/data/Shared/Date/ExcelToTimestamp1904.php b/tests/data/Shared/Date/ExcelToTimestamp1904.php
index 82fcde1cf..12a3999a9 100644
--- a/tests/data/Shared/Date/ExcelToTimestamp1904.php
+++ b/tests/data/Shared/Date/ExcelToTimestamp1904.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Excel DateTimeStamp        Result            Comments
 
 return [
diff --git a/tests/data/Shared/Date/FormatCodes.php b/tests/data/Shared/Date/FormatCodes.php
index b558874c5..8cd09172c 100644
--- a/tests/data/Shared/Date/FormatCodes.php
+++ b/tests/data/Shared/Date/FormatCodes.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Excel Format Code                     Result
 return [
     [
diff --git a/tests/data/Shared/Date/FormattedPHPToExcel1900.php b/tests/data/Shared/Date/FormattedPHPToExcel1900.php
index 459954e19..3040418bf 100644
--- a/tests/data/Shared/Date/FormattedPHPToExcel1900.php
+++ b/tests/data/Shared/Date/FormattedPHPToExcel1900.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Year   Month  Day  Hours  Minutes  Seconds  Result            Comments
 
 return [
diff --git a/tests/data/Shared/Date/TimestampToExcel1900.php b/tests/data/Shared/Date/TimestampToExcel1900.php
index fd94d44fc..6206a8984 100644
--- a/tests/data/Shared/Date/TimestampToExcel1900.php
+++ b/tests/data/Shared/Date/TimestampToExcel1900.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Unix TimeStamp   Result           Comments
 
 return [
diff --git a/tests/data/Shared/Date/TimestampToExcel1904.php b/tests/data/Shared/Date/TimestampToExcel1904.php
index 43659a940..24b714eef 100644
--- a/tests/data/Shared/Date/TimestampToExcel1904.php
+++ b/tests/data/Shared/Date/TimestampToExcel1904.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 // Excel DateTimeStamp  Result
 return [
     [
diff --git a/tests/data/Shared/FontSizeToPixels.php b/tests/data/Shared/FontSizeToPixels.php
index a222ec182..3b6e7f710 100644
--- a/tests/data/Shared/FontSizeToPixels.php
+++ b/tests/data/Shared/FontSizeToPixels.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         8,
diff --git a/tests/data/Shared/InchSizeToPixels.php b/tests/data/Shared/InchSizeToPixels.php
index f165460e8..1162addc2 100644
--- a/tests/data/Shared/InchSizeToPixels.php
+++ b/tests/data/Shared/InchSizeToPixels.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         9.5999999999999996,
diff --git a/tests/data/Shared/PasswordHashes.php b/tests/data/Shared/PasswordHashes.php
index c46adf142..5c697d22c 100644
--- a/tests/data/Shared/PasswordHashes.php
+++ b/tests/data/Shared/PasswordHashes.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'BCDE',
diff --git a/tests/data/Shared/Trend/ExponentialBestFit.php b/tests/data/Shared/Trend/ExponentialBestFit.php
index ac1da739c..04d8b89f5 100644
--- a/tests/data/Shared/Trend/ExponentialBestFit.php
+++ b/tests/data/Shared/Trend/ExponentialBestFit.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'slope' => [0.8, 0.813512072856517],
diff --git a/tests/data/Shared/Trend/LinearBestFit.php b/tests/data/Shared/Trend/LinearBestFit.php
index b1be2f9a5..046fdb6ee 100644
--- a/tests/data/Shared/Trend/LinearBestFit.php
+++ b/tests/data/Shared/Trend/LinearBestFit.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         'slope' => [-1.1, -1.1064189189190],
diff --git a/tests/data/Style/Color/ColorChangeBrightness.php b/tests/data/Style/Color/ColorChangeBrightness.php
index 1c552e157..6d9f03836 100644
--- a/tests/data/Style/Color/ColorChangeBrightness.php
+++ b/tests/data/Style/Color/ColorChangeBrightness.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     // RGBA
     [
diff --git a/tests/data/Style/Color/ColorGetBlue.php b/tests/data/Style/Color/ColorGetBlue.php
index ff4d9fb7a..83fbdc774 100644
--- a/tests/data/Style/Color/ColorGetBlue.php
+++ b/tests/data/Style/Color/ColorGetBlue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     // RGBA (hex)
     [
diff --git a/tests/data/Style/Color/ColorGetGreen.php b/tests/data/Style/Color/ColorGetGreen.php
index 5ab7b9dc7..d0e60d70e 100644
--- a/tests/data/Style/Color/ColorGetGreen.php
+++ b/tests/data/Style/Color/ColorGetGreen.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     // RGBA (hex)
     [
diff --git a/tests/data/Style/Color/ColorGetRed.php b/tests/data/Style/Color/ColorGetRed.php
index cad0f5c35..1187d4506 100644
--- a/tests/data/Style/Color/ColorGetRed.php
+++ b/tests/data/Style/Color/ColorGetRed.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     // RGBA (hex)
     [
diff --git a/tests/data/Style/NumberFormat.php b/tests/data/Style/NumberFormat.php
index 733f8c469..ae734178d 100644
--- a/tests/data/Style/NumberFormat.php
+++ b/tests/data/Style/NumberFormat.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
 
 //  value, format, result
diff --git a/tests/data/Style/NumberFormatDates.php b/tests/data/Style/NumberFormatDates.php
index 632b967e0..c1f8eb1b8 100644
--- a/tests/data/Style/NumberFormatDates.php
+++ b/tests/data/Style/NumberFormatDates.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     [
         '19-12-1960 01:30:00',
diff --git a/tests/data/Style/NumberFormatFractions.php b/tests/data/Style/NumberFormatFractions.php
index e7d4cfa69..4daafca2a 100644
--- a/tests/data/Style/NumberFormatFractions.php
+++ b/tests/data/Style/NumberFormatFractions.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 //  value, format, result
 
 return [