diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Fixtures/Validation/Article.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Fixtures/Validation/Article.php
index 5f28d0648f..a1ecee6d0b 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Fixtures/Validation/Article.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Fixtures/Validation/Article.php
@@ -2,9 +2,7 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Fixtures\Validation;
 
-if (!function_exists('__phpunit_run_isolated_test')) {
-    class Article implements NotExistingInterface
-    {
-        public $category;
-    }
+class Article implements NotExistingInterface
+{
+    public $category;
 }
diff --git a/src/Symfony/Component/Config/Tests/Fixtures/BadParent.php b/src/Symfony/Component/Config/Tests/Fixtures/BadParent.php
index 3f9720bb8a..68d7296ed8 100644
--- a/src/Symfony/Component/Config/Tests/Fixtures/BadParent.php
+++ b/src/Symfony/Component/Config/Tests/Fixtures/BadParent.php
@@ -2,8 +2,6 @@
 
 namespace Symfony\Component\Config\Tests\Fixtures;
 
-if (!function_exists('__phpunit_run_isolated_test')) {
-    class BadParent extends MissingParent
-    {
-    }
+class BadParent extends MissingParent
+{
 }
diff --git a/src/Symfony/Component/Debug/Tests/Fixtures/Throwing.php b/src/Symfony/Component/Debug/Tests/Fixtures/Throwing.php
index d338ca9d57..21e0aba17d 100644
--- a/src/Symfony/Component/Debug/Tests/Fixtures/Throwing.php
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/Throwing.php
@@ -1,5 +1,3 @@
 <?php
 
-if (!function_exists('__phpunit_run_isolated_test')) {
-    throw new \Exception('boo');
-}
+throw new \Exception('boo');
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/OptionalServiceClass.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/OptionalServiceClass.php
index 3337269590..7e9238f223 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Compiler/OptionalServiceClass.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/OptionalServiceClass.php
@@ -13,8 +13,6 @@ namespace Symfony\Component\DependencyInjection\Tests\Compiler;
 
 use Symfony\Bug\NotExistClass;
 
-if (!function_exists('__phpunit_run_isolated_test')) {
-    class OptionalServiceClass extends NotExistClass
-    {
-    }
+class OptionalServiceClass extends NotExistClass
+{
 }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/validresource.php b/src/Symfony/Component/Routing/Tests/Fixtures/validresource.php
index f59a234d65..482c80b29e 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/validresource.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/validresource.php
@@ -1,8 +1,5 @@
 <?php
 
-if (function_exists('__phpunit_run_isolated_test')) {
-    return;
-}
 /** @var $loader \Symfony\Component\Routing\Loader\PhpFileLoader */
 /** @var \Symfony\Component\Routing\RouteCollection $collection */
 $collection = $loader->import('validpattern.php');