diff --git a/composer.json b/composer.json
index 57da5a9ab33..fb3bc51b31e 100644
--- a/composer.json
+++ b/composer.json
@@ -113,10 +113,7 @@
     "autoload-dev": {
         "psr-4": {
             "ApiPlatform\\Core\\Tests\\": "tests/"
-        },
-        "classmap": [
-            "vendor/phpunit/phpunit/tests/"
-        ]
+        }
     },
     "extra": {
         "branch-alias": {
diff --git a/tests/Bridge/Symfony/Bundle/Test/Constraint/ArraySubsetTest.php b/tests/Bridge/Symfony/Bundle/Test/Constraint/ArraySubsetTest.php
index a88914d74f7..955cdb78594 100644
--- a/tests/Bridge/Symfony/Bundle/Test/Constraint/ArraySubsetTest.php
+++ b/tests/Bridge/Symfony/Bundle/Test/Constraint/ArraySubsetTest.php
@@ -14,17 +14,12 @@
 namespace ApiPlatform\Core\Tests\Bridge\Symfony\Bundle\Test\Constraint;
 
 use ApiPlatform\Core\Bridge\Symfony\Bundle\Test\Constraint\ArraySubset;
-use ArrayAccessible;
-use ArrayObject;
-use Countable;
+use ApiPlatform\Core\Tests\Fixtures\ArrayAccessible;
 use PHPUnit\Framework\ExpectationFailedException;
 use PHPUnit\Framework\SelfDescribing;
 use PHPUnit\Framework\TestCase;
 use PHPUnit\Runner\Version;
-use ReflectionClass;
 use SebastianBergmann\RecursionContext\InvalidArgumentException;
-use Traversable;
-use function sprintf;
 
 /**
  * Imported from dms/phpunit-arraysubset-asserts, because the original constraint has been deprecated.
@@ -64,12 +59,12 @@ public static function evaluateDataProvider(): array
             'loose array subset and ArrayObject other' => [
                 'expected' => true,
                 'subset' => ['bar' => 0],
-                'other' => new ArrayObject(['foo' => '', 'bar' => '0']),
+                'other' => new \ArrayObject(['foo' => '', 'bar' => '0']),
                 'strict' => false,
             ],
             'strict ArrayObject subset and array other' => [
                 'expected' => true,
-                'subset' => new ArrayObject(['bar' => 0]),
+                'subset' => new \ArrayObject(['bar' => 0]),
                 'other' => ['foo' => '', 'bar' => 0],
                 'strict' => true,
             ],
@@ -77,9 +72,9 @@ public static function evaluateDataProvider(): array
     }
 
     /**
-     * @param array|Traversable|mixed[] $subset
-     * @param array|Traversable|mixed[] $other
-     * @param bool                      $strict
+     * @param array|\Traversable|mixed[] $subset
+     * @param array|\Traversable|mixed[] $other
+     * @param bool                       $strict
      *
      * @throws ExpectationFailedException
      * @throws InvalidArgumentException
@@ -118,20 +113,20 @@ public function testEvaluateFailMessage(): void
 
     public function testIsCountable(): void
     {
-        $reflection = new ReflectionClass(ArraySubset::class);
+        $reflection = new \ReflectionClass(ArraySubset::class);
 
         $this->assertTrue(
-            $reflection->implementsInterface(Countable::class),
+            $reflection->implementsInterface(\Countable::class),
             sprintf(
                 'Failed to assert that ArraySubset implements "%s".',
-                Countable::class
+                \Countable::class
             )
         );
     }
 
     public function testIsSelfDescribing(): void
     {
-        $reflection = new ReflectionClass(ArraySubset::class);
+        $reflection = new \ReflectionClass(ArraySubset::class);
 
         $this->assertTrue(
             $reflection->implementsInterface(SelfDescribing::class),
diff --git a/tests/Fixtures/ArrayAccessible.php b/tests/Fixtures/ArrayAccessible.php
new file mode 100644
index 00000000000..92073f5d942
--- /dev/null
+++ b/tests/Fixtures/ArrayAccessible.php
@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the API Platform project.
+ *
+ * (c) Kévin Dunglas <dunglas@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace ApiPlatform\Core\Tests\Fixtures;
+
+class ArrayAccessible implements \ArrayAccess, \IteratorAggregate
+{
+    private $array;
+
+    public function __construct(array $array = [])
+    {
+        $this->array = $array;
+    }
+
+    public function offsetExists($offset)
+    {
+        return \array_key_exists($offset, $this->array);
+    }
+
+    public function offsetGet($offset)
+    {
+        return $this->array[$offset];
+    }
+
+    public function offsetSet($offset, $value): void
+    {
+        if (null === $offset) {
+            $this->array[] = $value;
+        } else {
+            $this->array[$offset] = $value;
+        }
+    }
+
+    public function offsetUnset($offset): void
+    {
+        unset($this->array[$offset]);
+    }
+
+    public function getIterator()
+    {
+        return new \ArrayIterator($this->array);
+    }
+}