diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
index ce2248640..20f6ed8d5 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingBasicTest.php
@@ -4,39 +4,30 @@ namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
 use PhpOffice\PhpSpreadsheet\Style\Conditional;
-use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use PHPUnit\Framework\TestCase;
 
 class ConditionalFormattingBasicTest extends TestCase
 {
-    /**
-     * @var Worksheet
-     */
-    protected $sheet;
-
-    protected function setUp(): void
-    {
-        $filename = 'tests/data/Reader/XLS/CF_Basic_Comparisons.xls';
-        $reader = new Xls();
-        $spreadsheet = $reader->load($filename);
-        $this->sheet = $spreadsheet->getActiveSheet();
-    }
-
     /**
      * @dataProvider conditionalFormattingProvider
      */
     public function testReadConditionalFormatting(string $expectedRange, array $expectedRules): void
     {
-        $hasConditionalStyles = $this->sheet->conditionalStylesExists($expectedRange);
+        $filename = 'tests/data/Reader/XLS/CF_Basic_Comparisons.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        $hasConditionalStyles = $sheet->conditionalStylesExists($expectedRange);
         self::assertTrue($hasConditionalStyles);
 
-        $conditionalStyles = $this->sheet->getConditionalStyles($expectedRange);
+        $conditionalStyles = $sheet->getConditionalStyles($expectedRange);
 
         foreach ($conditionalStyles as $index => $conditionalStyle) {
             self::assertSame($expectedRules[$index]['type'], $conditionalStyle->getConditionType());
             self::assertSame($expectedRules[$index]['operator'], $conditionalStyle->getOperatorType());
             self::assertSame($expectedRules[$index]['conditions'], $conditionalStyle->getConditions());
         }
+        $spreadsheet->disconnectWorksheets();
     }
 
     public function conditionalFormattingProvider(): array
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
index 6cc566c1f..a9cce8c32 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/ConditionalFormattingExpressionTest.php
@@ -4,39 +4,30 @@ namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
 use PhpOffice\PhpSpreadsheet\Style\Conditional;
-use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use PHPUnit\Framework\TestCase;
 
 class ConditionalFormattingExpressionTest extends TestCase
 {
-    /**
-     * @var Worksheet
-     */
-    protected $sheet;
-
-    protected function setUp(): void
-    {
-        $filename = 'tests/data/Reader/XLS/CF_Expression_Comparisons.xls';
-        $reader = new Xls();
-        $spreadsheet = $reader->load($filename);
-        $this->sheet = $spreadsheet->getActiveSheet();
-    }
-
     /**
      * @dataProvider conditionalFormattingProvider
      */
     public function testReadConditionalFormatting(string $expectedRange, array $expectedRule): void
     {
-        $hasConditionalStyles = $this->sheet->conditionalStylesExists($expectedRange);
+        $filename = 'tests/data/Reader/XLS/CF_Expression_Comparisons.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        $hasConditionalStyles = $sheet->conditionalStylesExists($expectedRange);
         self::assertTrue($hasConditionalStyles);
 
-        $conditionalStyles = $this->sheet->getConditionalStyles($expectedRange);
+        $conditionalStyles = $sheet->getConditionalStyles($expectedRange);
 
         foreach ($conditionalStyles as $index => $conditionalStyle) {
             self::assertSame($expectedRule[$index]['type'], $conditionalStyle->getConditionType());
             self::assertSame($expectedRule[$index]['operator'], $conditionalStyle->getOperatorType());
             self::assertSame($expectedRule[$index]['conditions'], $conditionalStyle->getConditions());
         }
+        $spreadsheet->disconnectWorksheets();
     }
 
     public function conditionalFormattingProvider(): array
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
index bdefa17e2..129fb96f1 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/DataValidationTest.php
@@ -4,36 +4,27 @@ namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Cell\DataValidation;
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
-use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use PHPUnit\Framework\TestCase;
 
 class DataValidationTest extends TestCase
 {
-    /**
-     * @var Worksheet
-     */
-    protected $sheet;
-
-    protected function setUp(): void
-    {
-        $filename = 'tests/data/Reader/XLS/DataValidation.xls';
-        $reader = new Xls();
-        $spreadsheet = $reader->load($filename);
-        $this->sheet = $spreadsheet->getActiveSheet();
-    }
-
     /**
      * @dataProvider dataValidationProvider
      */
     public function testDataValidation(string $expectedRange, array $expectedRule): void
     {
-        $hasDataValidation = $this->sheet->dataValidationExists($expectedRange);
+        $filename = 'tests/data/Reader/XLS/DataValidation.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        $hasDataValidation = $sheet->dataValidationExists($expectedRange);
         self::assertTrue($hasDataValidation);
 
-        $dataValidation = $this->sheet->getDataValidation($expectedRange);
+        $dataValidation = $sheet->getDataValidation($expectedRange);
         self::assertSame($expectedRule['type'], $dataValidation->getType());
         self::assertSame($expectedRule['operator'], $dataValidation->getOperator());
         self::assertSame($expectedRule['formula'], $dataValidation->getFormula1());
+        $spreadsheet->disconnectWorksheets();
     }
 
     public function dataValidationProvider(): array
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php
new file mode 100644
index 000000000..c27972054
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/FormulasTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
+
+use PhpOffice\PhpSpreadsheet\Reader\Xls;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class FormulasTest extends AbstractFunctional
+{
+    public function testFormulas(): void
+    {
+        // This file was created with Excel 365.
+        $filename = 'tests/data/Reader/XLS/formulas.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        $originalArray = $sheet->toArray(null, false, false, false);
+
+        $newSpreadsheet = $this->writeAndReload($spreadsheet, 'Xls');
+        $spreadsheet->disconnectWorksheets();
+        $newWorksheet = $newSpreadsheet->getActiveSheet();
+        $newArray = $newWorksheet->toArray(null, false, false, false);
+        self::assertSame($originalArray, $newArray);
+        $newSpreadsheet->disconnectWorksheets();
+    }
+
+    public function testDatabaseFormulas(): void
+    {
+        // This file was created with Excel 2003.
+        $filename = 'tests/data/Reader/XLS/formulas.database.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
+        $sheet = $spreadsheet->getActiveSheet();
+        $originalArray = $sheet->toArray(null, false, false, false);
+
+        $newSpreadsheet = $this->writeAndReload($spreadsheet, 'Xls');
+        $spreadsheet->disconnectWorksheets();
+        $newWorksheet = $newSpreadsheet->getActiveSheet();
+        $newArray = $newWorksheet->toArray(null, false, false, false);
+        self::assertSame($originalArray, $newArray);
+        $newSpreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
index e31b38804..aa50599c3 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/HiddenWorksheetTest.php
@@ -15,9 +15,11 @@ class HiddenWorksheetTest extends TestCase
         $spreadsheet = $reader->load($filename);
         $assertions = $this->worksheetAssertions();
 
+        $sheetCount = 0;
         foreach ($spreadsheet->getAllSheets() as $worksheet) {
+            ++$sheetCount;
             if (!array_key_exists($worksheet->getTitle(), $assertions)) {
-                continue;
+                self::fail('Unexpected worksheet' . $worksheet->getTitle());
             }
 
             $sheetAssertions = $assertions[$worksheet->getTitle()];
@@ -30,6 +32,7 @@ class HiddenWorksheetTest extends TestCase
                 );
             }
         }
+        self::assertCount($sheetCount, $assertions);
         $spreadsheet->disconnectWorksheets();
     }
 
diff --git a/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php b/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
index 034ce6ee7..f90595465 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xls/PageSetupTest.php
@@ -3,7 +3,6 @@
 namespace PhpOffice\PhpSpreadsheetTests\Reader\Xls;
 
 use PhpOffice\PhpSpreadsheet\Reader\Xls;
-use PhpOffice\PhpSpreadsheet\Spreadsheet;
 use PhpOffice\PhpSpreadsheet\Worksheet\PageSetup;
 use PHPUnit\Framework\TestCase;
 
@@ -13,25 +12,18 @@ class PageSetupTest extends TestCase
 
     private const MARGIN_UNIT_CONVERSION = 2.54; // Inches to cm
 
-    /**
-     * @var Spreadsheet
-     */
-    private $spreadsheet;
-
-    protected function setup(): void
+    public function testPageSetup(): void
     {
         $filename = 'tests/data/Reader/XLS/PageSetup.xls';
         $reader = new Xls();
-        $this->spreadsheet = $reader->load($filename);
-    }
-
-    public function testPageSetup(): void
-    {
+        $spreadsheet = $reader->load($filename);
         $assertions = $this->pageSetupAssertions();
 
-        foreach ($this->spreadsheet->getAllSheets() as $worksheet) {
+        $sheetCount = 0;
+        foreach ($spreadsheet->getAllSheets() as $worksheet) {
+            ++$sheetCount;
             if (!array_key_exists($worksheet->getTitle(), $assertions)) {
-                continue;
+                self::fail('Unexpected worksheet ' . $worksheet->getTitle());
             }
 
             $sheetAssertions = $assertions[$worksheet->getTitle()];
@@ -45,15 +37,22 @@ class PageSetupTest extends TestCase
                 );
             }
         }
+        self::assertCount($sheetCount, $assertions);
+        $spreadsheet->disconnectWorksheets();
     }
 
     public function testPageMargins(): void
     {
+        $filename = 'tests/data/Reader/XLS/PageSetup.xls';
+        $reader = new Xls();
+        $spreadsheet = $reader->load($filename);
         $assertions = $this->pageMarginAssertions();
 
-        foreach ($this->spreadsheet->getAllSheets() as $worksheet) {
+        $sheetCount = 0;
+        foreach ($spreadsheet->getAllSheets() as $worksheet) {
+            ++$sheetCount;
             if (!array_key_exists($worksheet->getTitle(), $assertions)) {
-                continue;
+                self::fail('Unexpected worksheet ' . $worksheet->getTitle());
             }
 
             $sheetAssertions = $assertions[$worksheet->getTitle()];
@@ -68,6 +67,8 @@ class PageSetupTest extends TestCase
                 );
             }
         }
+        self::assertCount($sheetCount, $assertions);
+        $spreadsheet->disconnectWorksheets();
     }
 
     private function pageSetupAssertions(): array
diff --git a/tests/data/Reader/XLS/formulas.database.xls b/tests/data/Reader/XLS/formulas.database.xls
new file mode 100644
index 000000000..bd18d0eb5
Binary files /dev/null and b/tests/data/Reader/XLS/formulas.database.xls differ
diff --git a/tests/data/Reader/XLS/formulas.xls b/tests/data/Reader/XLS/formulas.xls
new file mode 100644
index 000000000..e18c80e69
Binary files /dev/null and b/tests/data/Reader/XLS/formulas.xls differ