diff --git a/CHANGELOG b/CHANGELOG
index d36aa696f..23970440b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 # 3.21.0 (2025-XX-XX)
 
+ * Fix testing and expression when it evaluates to an instance of `Markup`
+ * Add `ReturnPrimitiveTypeInterface` (and sub-interfaces for number, boolean, string, and array)
  * Add `SupportDefinedTestInterface` for expression nodes supporting the `defined` test
  * Deprecate using the `|` operator in an expression with `+` or `-` without using parentheses to clarify precedence
  * Deprecate operator precedence outside of the [0, 512] range
diff --git a/src/Extension/CoreExtension.php b/src/Extension/CoreExtension.php
index f44b6ad6d..e41b5ba3c 100644
--- a/src/Extension/CoreExtension.php
+++ b/src/Extension/CoreExtension.php
@@ -76,6 +76,7 @@ use Twig\Node\Expression\Test\EvenTest;
 use Twig\Node\Expression\Test\NullTest;
 use Twig\Node\Expression\Test\OddTest;
 use Twig\Node\Expression\Test\SameasTest;
+use Twig\Node\Expression\Test\TrueTest;
 use Twig\Node\Expression\Unary\NegUnary;
 use Twig\Node\Expression\Unary\NotUnary;
 use Twig\Node\Expression\Unary\PosUnary;
@@ -318,6 +319,7 @@ final class CoreExtension extends AbstractExtension
             new TwigTest('iterable', 'is_iterable'),
             new TwigTest('sequence', [self::class, 'testSequence']),
             new TwigTest('mapping', [self::class, 'testMapping']),
+            new TwigTest('true', null, ['node_class' => TrueTest::class]),
         ];
     }
 
diff --git a/src/Node/Expression/ArrayExpression.php b/src/Node/Expression/ArrayExpression.php
index e58f43c91..9678be26c 100644
--- a/src/Node/Expression/ArrayExpression.php
+++ b/src/Node/Expression/ArrayExpression.php
@@ -16,7 +16,7 @@ use Twig\Node\Expression\Unary\SpreadUnary;
 use Twig\Node\Expression\Unary\StringCastUnary;
 use Twig\Node\Expression\Variable\ContextVariable;
 
-class ArrayExpression extends AbstractExpression implements SupportDefinedTestInterface
+class ArrayExpression extends AbstractExpression implements SupportDefinedTestInterface, ReturnArrayInterface
 {
     use SupportDefinedTestTrait;
 
diff --git a/src/Node/Expression/Binary/AddBinary.php b/src/Node/Expression/Binary/AddBinary.php
index ee4307e33..42377aea0 100644
--- a/src/Node/Expression/Binary/AddBinary.php
+++ b/src/Node/Expression/Binary/AddBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class AddBinary extends AbstractBinary
+class AddBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/AndBinary.php b/src/Node/Expression/Binary/AndBinary.php
index 5f2380da5..454ea70e5 100644
--- a/src/Node/Expression/Binary/AndBinary.php
+++ b/src/Node/Expression/Binary/AndBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class AndBinary extends AbstractBinary
+class AndBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/BitwiseAndBinary.php b/src/Node/Expression/Binary/BitwiseAndBinary.php
index db7d6d612..1c26f9893 100644
--- a/src/Node/Expression/Binary/BitwiseAndBinary.php
+++ b/src/Node/Expression/Binary/BitwiseAndBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class BitwiseAndBinary extends AbstractBinary
+class BitwiseAndBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/BitwiseOrBinary.php b/src/Node/Expression/Binary/BitwiseOrBinary.php
index ce803dd90..ec17e2280 100644
--- a/src/Node/Expression/Binary/BitwiseOrBinary.php
+++ b/src/Node/Expression/Binary/BitwiseOrBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class BitwiseOrBinary extends AbstractBinary
+class BitwiseOrBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/BitwiseXorBinary.php b/src/Node/Expression/Binary/BitwiseXorBinary.php
index 5c2978501..e6432a7ae 100644
--- a/src/Node/Expression/Binary/BitwiseXorBinary.php
+++ b/src/Node/Expression/Binary/BitwiseXorBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class BitwiseXorBinary extends AbstractBinary
+class BitwiseXorBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/ConcatBinary.php b/src/Node/Expression/Binary/ConcatBinary.php
index f825ab874..75ee65473 100644
--- a/src/Node/Expression/Binary/ConcatBinary.php
+++ b/src/Node/Expression/Binary/ConcatBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnStringInterface;
 
-class ConcatBinary extends AbstractBinary
+class ConcatBinary extends AbstractBinary implements ReturnStringInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/DivBinary.php b/src/Node/Expression/Binary/DivBinary.php
index e3817d1cd..11c061e18 100644
--- a/src/Node/Expression/Binary/DivBinary.php
+++ b/src/Node/Expression/Binary/DivBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class DivBinary extends AbstractBinary
+class DivBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/EndsWithBinary.php b/src/Node/Expression/Binary/EndsWithBinary.php
index a73a5608d..e689d668a 100644
--- a/src/Node/Expression/Binary/EndsWithBinary.php
+++ b/src/Node/Expression/Binary/EndsWithBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class EndsWithBinary extends AbstractBinary
+class EndsWithBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/EqualBinary.php b/src/Node/Expression/Binary/EqualBinary.php
index 5f423196f..8c3650355 100644
--- a/src/Node/Expression/Binary/EqualBinary.php
+++ b/src/Node/Expression/Binary/EqualBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class EqualBinary extends AbstractBinary
+class EqualBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/FloorDivBinary.php b/src/Node/Expression/Binary/FloorDivBinary.php
index d7e7980ef..a60ab3b21 100644
--- a/src/Node/Expression/Binary/FloorDivBinary.php
+++ b/src/Node/Expression/Binary/FloorDivBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class FloorDivBinary extends AbstractBinary
+class FloorDivBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/GreaterBinary.php b/src/Node/Expression/Binary/GreaterBinary.php
index f42de3f86..71a980b3e 100644
--- a/src/Node/Expression/Binary/GreaterBinary.php
+++ b/src/Node/Expression/Binary/GreaterBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class GreaterBinary extends AbstractBinary
+class GreaterBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/GreaterEqualBinary.php b/src/Node/Expression/Binary/GreaterEqualBinary.php
index 0c4f43fd9..c92e61b37 100644
--- a/src/Node/Expression/Binary/GreaterEqualBinary.php
+++ b/src/Node/Expression/Binary/GreaterEqualBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class GreaterEqualBinary extends AbstractBinary
+class GreaterEqualBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/HasEveryBinary.php b/src/Node/Expression/Binary/HasEveryBinary.php
index c57bb20e9..22b380118 100644
--- a/src/Node/Expression/Binary/HasEveryBinary.php
+++ b/src/Node/Expression/Binary/HasEveryBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class HasEveryBinary extends AbstractBinary
+class HasEveryBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/HasSomeBinary.php b/src/Node/Expression/Binary/HasSomeBinary.php
index 12293f84c..a2a363e99 100644
--- a/src/Node/Expression/Binary/HasSomeBinary.php
+++ b/src/Node/Expression/Binary/HasSomeBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class HasSomeBinary extends AbstractBinary
+class HasSomeBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/InBinary.php b/src/Node/Expression/Binary/InBinary.php
index 68a98fe15..31a21e7d6 100644
--- a/src/Node/Expression/Binary/InBinary.php
+++ b/src/Node/Expression/Binary/InBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class InBinary extends AbstractBinary
+class InBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/LessBinary.php b/src/Node/Expression/Binary/LessBinary.php
index fb3264a2d..293d98d51 100644
--- a/src/Node/Expression/Binary/LessBinary.php
+++ b/src/Node/Expression/Binary/LessBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class LessBinary extends AbstractBinary
+class LessBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/LessEqualBinary.php b/src/Node/Expression/Binary/LessEqualBinary.php
index 8f3653892..239d9fdfe 100644
--- a/src/Node/Expression/Binary/LessEqualBinary.php
+++ b/src/Node/Expression/Binary/LessEqualBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class LessEqualBinary extends AbstractBinary
+class LessEqualBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/MatchesBinary.php b/src/Node/Expression/Binary/MatchesBinary.php
index 0a523c216..32e8d34e4 100644
--- a/src/Node/Expression/Binary/MatchesBinary.php
+++ b/src/Node/Expression/Binary/MatchesBinary.php
@@ -13,10 +13,11 @@ namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
 use Twig\Error\SyntaxError;
+use Twig\Node\Expression\ReturnBoolInterface;
 use Twig\Node\Expression\ConstantExpression;
 use Twig\Node\Node;
 
-class MatchesBinary extends AbstractBinary
+class MatchesBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function __construct(Node $left, Node $right, int $lineno)
     {
diff --git a/src/Node/Expression/Binary/ModBinary.php b/src/Node/Expression/Binary/ModBinary.php
index 271b45cac..aef48f3d0 100644
--- a/src/Node/Expression/Binary/ModBinary.php
+++ b/src/Node/Expression/Binary/ModBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class ModBinary extends AbstractBinary
+class ModBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/MulBinary.php b/src/Node/Expression/Binary/MulBinary.php
index 6d4c1e0b6..beb881ae3 100644
--- a/src/Node/Expression/Binary/MulBinary.php
+++ b/src/Node/Expression/Binary/MulBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class MulBinary extends AbstractBinary
+class MulBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/NotEqualBinary.php b/src/Node/Expression/Binary/NotEqualBinary.php
index d137ef627..fd24ef911 100644
--- a/src/Node/Expression/Binary/NotEqualBinary.php
+++ b/src/Node/Expression/Binary/NotEqualBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class NotEqualBinary extends AbstractBinary
+class NotEqualBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/NotInBinary.php b/src/Node/Expression/Binary/NotInBinary.php
index 80c8755d8..9fd27311f 100644
--- a/src/Node/Expression/Binary/NotInBinary.php
+++ b/src/Node/Expression/Binary/NotInBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class NotInBinary extends AbstractBinary
+class NotInBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/OrBinary.php b/src/Node/Expression/Binary/OrBinary.php
index 21f87c91b..82dcb7e95 100644
--- a/src/Node/Expression/Binary/OrBinary.php
+++ b/src/Node/Expression/Binary/OrBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class OrBinary extends AbstractBinary
+class OrBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/PowerBinary.php b/src/Node/Expression/Binary/PowerBinary.php
index c9f4c6697..5325e8eb0 100644
--- a/src/Node/Expression/Binary/PowerBinary.php
+++ b/src/Node/Expression/Binary/PowerBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class PowerBinary extends AbstractBinary
+class PowerBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/RangeBinary.php b/src/Node/Expression/Binary/RangeBinary.php
index 55982c819..f318d8e55 100644
--- a/src/Node/Expression/Binary/RangeBinary.php
+++ b/src/Node/Expression/Binary/RangeBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnArrayInterface;
 
-class RangeBinary extends AbstractBinary
+class RangeBinary extends AbstractBinary implements ReturnArrayInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/SpaceshipBinary.php b/src/Node/Expression/Binary/SpaceshipBinary.php
index ae5a4a493..c0a28b0a8 100644
--- a/src/Node/Expression/Binary/SpaceshipBinary.php
+++ b/src/Node/Expression/Binary/SpaceshipBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class SpaceshipBinary extends AbstractBinary
+class SpaceshipBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/StartsWithBinary.php b/src/Node/Expression/Binary/StartsWithBinary.php
index 4519f30d9..ef2fc9502 100644
--- a/src/Node/Expression/Binary/StartsWithBinary.php
+++ b/src/Node/Expression/Binary/StartsWithBinary.php
@@ -12,8 +12,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class StartsWithBinary extends AbstractBinary
+class StartsWithBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function compile(Compiler $compiler): void
     {
diff --git a/src/Node/Expression/Binary/SubBinary.php b/src/Node/Expression/Binary/SubBinary.php
index eeb87faca..10663f5c1 100644
--- a/src/Node/Expression/Binary/SubBinary.php
+++ b/src/Node/Expression/Binary/SubBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnNumberInterface;
 
-class SubBinary extends AbstractBinary
+class SubBinary extends AbstractBinary implements ReturnNumberInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/Binary/XorBinary.php b/src/Node/Expression/Binary/XorBinary.php
index d8ccd7853..6f412d22f 100644
--- a/src/Node/Expression/Binary/XorBinary.php
+++ b/src/Node/Expression/Binary/XorBinary.php
@@ -13,8 +13,9 @@
 namespace Twig\Node\Expression\Binary;
 
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnBoolInterface;
 
-class XorBinary extends AbstractBinary
+class XorBinary extends AbstractBinary implements ReturnBoolInterface
 {
     public function operator(Compiler $compiler): Compiler
     {
diff --git a/src/Node/Expression/ConstantExpression.php b/src/Node/Expression/ConstantExpression.php
index 8f8b2ffe9..12dc0621f 100644
--- a/src/Node/Expression/ConstantExpression.php
+++ b/src/Node/Expression/ConstantExpression.php
@@ -17,7 +17,7 @@ use Twig\Compiler;
 /**
  * @final
  */
-class ConstantExpression extends AbstractExpression implements SupportDefinedTestInterface
+class ConstantExpression extends AbstractExpression implements SupportDefinedTestInterface, ReturnPrimitiveTypeInterface
 {
     use SupportDefinedTestTrait;
 
diff --git a/src/Node/Expression/ReturnArrayInterface.php b/src/Node/Expression/ReturnArrayInterface.php
new file mode 100644
index 000000000..a74864b5d
--- /dev/null
+++ b/src/Node/Expression/ReturnArrayInterface.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression;
+
+interface ReturnArrayInterface extends ReturnPrimitiveTypeInterface
+{
+}
diff --git a/src/Node/Expression/ReturnBoolInterface.php b/src/Node/Expression/ReturnBoolInterface.php
new file mode 100644
index 000000000..7046946c7
--- /dev/null
+++ b/src/Node/Expression/ReturnBoolInterface.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression;
+
+interface ReturnBoolInterface extends ReturnPrimitiveTypeInterface
+{
+}
diff --git a/src/Node/Expression/ReturnNumberInterface.php b/src/Node/Expression/ReturnNumberInterface.php
new file mode 100644
index 000000000..8ae3b3d34
--- /dev/null
+++ b/src/Node/Expression/ReturnNumberInterface.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression;
+
+interface ReturnNumberInterface extends ReturnPrimitiveTypeInterface
+{
+}
diff --git a/src/Node/Expression/ReturnPrimitiveTypeInterface.php b/src/Node/Expression/ReturnPrimitiveTypeInterface.php
new file mode 100644
index 000000000..6b87b8b12
--- /dev/null
+++ b/src/Node/Expression/ReturnPrimitiveTypeInterface.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression;
+
+interface ReturnPrimitiveTypeInterface
+{
+}
diff --git a/src/Node/Expression/ReturnStringInterface.php b/src/Node/Expression/ReturnStringInterface.php
new file mode 100644
index 000000000..53d29aabe
--- /dev/null
+++ b/src/Node/Expression/ReturnStringInterface.php
@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression;
+
+interface ReturnStringInterface extends ReturnPrimitiveTypeInterface
+{
+}
diff --git a/src/Node/Expression/Ternary/ConditionalTernary.php b/src/Node/Expression/Ternary/ConditionalTernary.php
index 627da7a43..f7cd78c5c 100644
--- a/src/Node/Expression/Ternary/ConditionalTernary.php
+++ b/src/Node/Expression/Ternary/ConditionalTernary.php
@@ -14,11 +14,18 @@ namespace Twig\Node\Expression\Ternary;
 use Twig\Compiler;
 use Twig\Node\Expression\AbstractExpression;
 use Twig\Node\Expression\OperatorEscapeInterface;
+use Twig\Node\Expression\ReturnPrimitiveTypeInterface;
+use Twig\Node\Expression\Test\TrueTest;
+use Twig\TwigTest;
 
 final class ConditionalTernary extends AbstractExpression implements OperatorEscapeInterface
 {
     public function __construct(AbstractExpression $test, AbstractExpression $left, AbstractExpression $right, int $lineno)
     {
+        if (!$test instanceof ReturnPrimitiveTypeInterface) {
+            $test = new TrueTest($test, new TwigTest('true'), null, $test->getTemplateLine());
+        }
+
         parent::__construct(['test' => $test, 'left' => $left, 'right' => $right], [], $lineno);
     }
 
diff --git a/src/Node/Expression/Test/NullTest.php b/src/Node/Expression/Test/NullTest.php
index 45b54ae37..be5d38891 100644
--- a/src/Node/Expression/Test/NullTest.php
+++ b/src/Node/Expression/Test/NullTest.php
@@ -15,7 +15,7 @@ use Twig\Compiler;
 use Twig\Node\Expression\TestExpression;
 
 /**
- * Checks that a variable is null.
+ * Checks that an expression is null.
  *
  *  {{ var is none }}
  *
diff --git a/src/Node/Expression/Test/TrueTest.php b/src/Node/Expression/Test/TrueTest.php
new file mode 100644
index 000000000..22186a689
--- /dev/null
+++ b/src/Node/Expression/Test/TrueTest.php
@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Node\Expression\Test;
+
+use Twig\Compiler;
+use Twig\Node\Expression\TestExpression;
+
+/**
+ * Checks that an expression is true.
+ *
+ *  {{ var is true }}
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class TrueTest extends TestExpression
+{
+    public function compile(Compiler $compiler): void
+    {
+        $compiler
+            ->raw('(($tmp = ')
+            ->subcompile($this->getNode('node'))
+            ->raw(') && $tmp instanceof Markup ? (string) $tmp : $tmp)')
+        ;
+    }
+}
diff --git a/src/Node/Expression/TestExpression.php b/src/Node/Expression/TestExpression.php
index 27e1526a1..3b51dd320 100644
--- a/src/Node/Expression/TestExpression.php
+++ b/src/Node/Expression/TestExpression.php
@@ -17,7 +17,7 @@ use Twig\Node\NameDeprecation;
 use Twig\Node\Node;
 use Twig\TwigTest;
 
-class TestExpression extends CallExpression
+class TestExpression extends CallExpression implements ReturnBoolInterface
 {
     #[FirstClassTwigCallableReady]
     /**
diff --git a/src/Node/IfNode.php b/src/Node/IfNode.php
index 2af48fa81..2c0e2a8e9 100644
--- a/src/Node/IfNode.php
+++ b/src/Node/IfNode.php
@@ -14,6 +14,9 @@ namespace Twig\Node;
 
 use Twig\Attribute\YieldReady;
 use Twig\Compiler;
+use Twig\Node\Expression\ReturnPrimitiveTypeInterface;
+use Twig\Node\Expression\Test\TrueTest;
+use Twig\TwigTest;
 
 /**
  * Represents an if node.
@@ -25,6 +28,12 @@ class IfNode extends Node
 {
     public function __construct(Node $tests, ?Node $else, int $lineno)
     {
+        for ($i = 0, $count = \count($tests); $i < $count; $i += 2) {
+            $test = $tests->getNode((string) $i);
+            if (!$test instanceof ReturnPrimitiveTypeInterface) {
+                $tests->setNode($i, new TrueTest($test, new TwigTest('true'), null, $test->getTemplateLine()));
+            }
+        }
         $nodes = ['tests' => $tests];
         if (null !== $else) {
             $nodes['else'] = $else;
diff --git a/tests/Fixtures/regression/markup_test.test b/tests/Fixtures/regression/markup_test.test
new file mode 100644
index 000000000..e03c5291b
--- /dev/null
+++ b/tests/Fixtures/regression/markup_test.test
@@ -0,0 +1,18 @@
+--TEST--
+Twig outputs 0 nodes correctly
+--TEMPLATE--
+{{ empty|trim ? 'KO' : 'ok' }}
+{{ spaces|trim ? 'KO' : 'ok' }}
+{% if empty %}KO{% else %}ok{% endif %}
+
+{% if spaces|trim %}KO{% else %}ok{% endif %}
+
+{% set bar %}    {% endset %}{{ bar|trim ? 'KO' : 'ok' }}
+--DATA--
+return ['spaces' => new Twig\Markup('    ', 'UTF-8'), 'empty' => new Twig\Markup('', 'UTF-8')]
+--EXPECT--
+ok
+ok
+ok
+ok
+ok