diff --git a/core/phpstan.neon.dist b/core/phpstan.neon.dist
index f7e1f0e2932..7356bcddb91 100644
--- a/core/phpstan.neon.dist
+++ b/core/phpstan.neon.dist
@@ -41,7 +41,6 @@ parameters:
     - modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/ExtendingNonInstalledClass.php
     - modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/UsingNonInstalledTraitClass.php
     - modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/custom_annotation/ExtendingNonInstalledClass.php
-    - tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest2.php
 
   ignoreErrors:
     # new static() is a best practice in Drupal, so we cannot fix that.
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryCachedTest.php b/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryCachedTest.php
index 2b2f0c25abd..b3d11614cce 100644
--- a/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryCachedTest.php
+++ b/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryCachedTest.php
@@ -29,10 +29,10 @@ class AttributeClassDiscoveryCachedTest extends TestCase {
     FileCacheFactory::setPrefix('prefix');
 
     // Normally the attribute classes would be autoloaded.
-    include_once __DIR__ . '/Fixtures/CustomPlugin.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/CustomPlugin.php';
 
     $additionalClassLoader = new ClassLoader();
-    $additionalClassLoader->addPsr4("com\\example\\PluginNamespace\\", __DIR__ . "/Fixtures/Plugins/PluginNamespace");
+    $additionalClassLoader->addPsr4("com\\example\\PluginNamespace\\", __DIR__ . "/../../../../../fixtures/plugins/Plugin/PluginNamespace");
     $additionalClassLoader->register(TRUE);
   }
 
@@ -43,7 +43,7 @@ class AttributeClassDiscoveryCachedTest extends TestCase {
    */
   public function testGetDefinitions(): void {
     // Path to the classes which we'll discover and parse annotation.
-    $discovery_path = __DIR__ . '/Fixtures/Plugins';
+    $discovery_path = __DIR__ . "/../../../../../fixtures/plugins/Plugin";
     // File path that should be discovered within that directory.
     $file_path = $discovery_path . '/PluginNamespace/AttributeDiscoveryTest1.php';
     // Define a file path within the directory that should not be discovered.
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryTest.php b/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryTest.php
index 727405f4b90..aa20f8146f8 100644
--- a/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Component/Plugin/Attribute/AttributeClassDiscoveryTest.php
@@ -8,8 +8,6 @@ use Composer\Autoload\ClassLoader;
 use Drupal\Component\Plugin\Discovery\AttributeClassDiscovery;
 use Drupal\Component\FileCache\FileCacheFactory;
 use PHPUnit\Framework\TestCase;
-use com\example\PluginNamespace\CustomPlugin;
-use com\example\PluginNamespace\CustomPlugin2;
 
 /**
  * @coversDefaultClass \Drupal\Component\Plugin\Discovery\AttributeClassDiscovery
@@ -30,10 +28,10 @@ class AttributeClassDiscoveryTest extends TestCase {
     FileCacheFactory::setPrefix('prefix');
 
     // Normally the attribute classes would be autoloaded.
-    include_once __DIR__ . '/Fixtures/CustomPlugin.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/CustomPlugin.php';
 
     $additionalClassLoader = new ClassLoader();
-    $additionalClassLoader->addPsr4("com\\example\\PluginNamespace\\", __DIR__ . "/Fixtures/Plugins/PluginNamespace");
+    $additionalClassLoader->addPsr4("com\\example\\PluginNamespace\\", __DIR__ . "/../../../../../fixtures/plugins/Plugin/PluginNamespace");
     $additionalClassLoader->register(TRUE);
   }
 
@@ -57,7 +55,7 @@ class AttributeClassDiscoveryTest extends TestCase {
    * @covers ::prepareAttributeDefinition
    */
   public function testGetDefinitions(): void {
-    $discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . '/Fixtures/Plugins']]);
+    $discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . "/../../../../../fixtures/plugins/Plugin"]]);
     $this->assertEquals([
       'discovery_test_1' => [
         'id' => 'discovery_test_1',
@@ -65,7 +63,7 @@ class AttributeClassDiscoveryTest extends TestCase {
       ],
     ], $discovery->getDefinitions());
 
-    $custom_annotation_discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . '/Fixtures/Plugins']], CustomPlugin::class);
+    $custom_annotation_discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . "/../../../../../fixtures/plugins/Plugin"]], 'com\example\PluginNamespace\CustomPlugin');
     $this->assertEquals([
       'discovery_test_1' => [
         'id' => 'discovery_test_1',
@@ -74,7 +72,7 @@ class AttributeClassDiscoveryTest extends TestCase {
       ],
     ], $custom_annotation_discovery->getDefinitions());
 
-    $empty_discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . '/Fixtures/Plugins']], CustomPlugin2::class);
+    $empty_discovery = new AttributeClassDiscovery(['com\example' => [__DIR__ . "/../../../../../fixtures/plugins/Plugin"]], 'com\example\PluginNamespace\CustomPlugin2');
     $this->assertEquals([], $empty_discovery->getDefinitions());
   }
 
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Discovery/AttributeBridgeDecoratorTest.php b/core/tests/Drupal/Tests/Component/Plugin/Discovery/AttributeBridgeDecoratorTest.php
index d2deaa5ffb2..0772e684541 100644
--- a/core/tests/Drupal/Tests/Component/Plugin/Discovery/AttributeBridgeDecoratorTest.php
+++ b/core/tests/Drupal/Tests/Component/Plugin/Discovery/AttributeBridgeDecoratorTest.php
@@ -21,8 +21,8 @@ class AttributeBridgeDecoratorTest extends TestCase {
    */
   public function testGetDefinitions(): void {
     // Normally the attribute classes would be autoloaded.
-    include_once __DIR__ . '/../Attribute/Fixtures/CustomPlugin.php';
-    include_once __DIR__ . '/../Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest1.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/CustomPlugin.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest1.php';
 
     $definitions = [];
     $definitions['object'] = new ObjectDefinition(['id' => 'foo']);
@@ -51,8 +51,8 @@ class AttributeBridgeDecoratorTest extends TestCase {
    */
   public function testOtherMethod(): void {
     // Normally the attribute classes would be autoloaded.
-    include_once __DIR__ . '/../Attribute/Fixtures/CustomPlugin.php';
-    include_once __DIR__ . '/../Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest1.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/CustomPlugin.php';
+    include_once __DIR__ . '/../../../../../fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest1.php';
 
     $discovery = $this->createMock(ExtendedDiscoveryInterface::class);
     $discovery->expects($this->exactly(2))
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/CustomPlugin.php b/core/tests/fixtures/plugins/CustomPlugin.php
similarity index 100%
rename from core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/CustomPlugin.php
rename to core/tests/fixtures/plugins/CustomPlugin.php
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest1.php b/core/tests/fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest1.php
similarity index 100%
rename from core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest1.php
rename to core/tests/fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest1.php
diff --git a/core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest2.php b/core/tests/fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest2.php
similarity index 100%
rename from core/tests/Drupal/Tests/Component/Plugin/Attribute/Fixtures/Plugins/PluginNamespace/AttributeDiscoveryTest2.php
rename to core/tests/fixtures/plugins/Plugin/PluginNamespace/AttributeDiscoveryTest2.php