diff --git a/resources/config/test.xml b/resources/config/test.xml
deleted file mode 100644
index 528d18b..0000000
--- a/resources/config/test.xml
+++ /dev/null
@@ -1,41 +0,0 @@
-<?xml version="1.0" ?>
-
-<container xmlns="http://symfony.com/schema/dic/services"
-           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-           xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
-
-    <parameters>
-        <parameter key="test.client.parameters" type="collection"></parameter>
-    </parameters>
-
-    <services>
-        <defaults public="false" />
-
-        <service id="test.client" class="Symfony\Bundle\FrameworkBundle\KernelBrowser" shared="false" public="true">
-            <argument type="service" id="kernel" />
-            <argument>%test.client.parameters%</argument>
-            <argument type="service" id="test.client.history" />
-            <argument type="service" id="test.client.cookiejar" />
-        </service>
-
-        <service id="test.client.history" class="Symfony\Component\BrowserKit\History" shared="false" />
-
-        <service id="test.client.cookiejar" class="Symfony\Component\BrowserKit\CookieJar" shared="false" />
-
-        <service id="test.session.listener" class="Symfony\Component\HttpKernel\EventListener\TestSessionListener">
-            <tag name="kernel.event_subscriber" />
-            <argument type="service_locator">
-                <argument key="session" type="service" id="session" on-invalid="ignore" />
-            </argument>
-        </service>
-
-        <service id="test.service_container" class="Symfony\Bundle\FrameworkBundle\Test\TestContainer" public="true">
-            <argument type="service" id="kernel" />
-            <argument>test.private_services_locator</argument>
-        </service>
-
-        <service id="test.private_services_locator" class="Symfony\Component\DependencyInjection\ServiceLocator" public="true">
-            <argument type="collection" />
-        </service>
-    </services>
-</container>
diff --git a/src/DependencyInjection/PsyshExtension.php b/src/DependencyInjection/PsyshExtension.php
index f61fe24..949b536 100644
--- a/src/DependencyInjection/PsyshExtension.php
+++ b/src/DependencyInjection/PsyshExtension.php
@@ -14,6 +14,7 @@
 use Psy\Command\Command;
 use Symfony\Component\Config\FileLocator;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Extension\PrependExtensionInterface;
 use Symfony\Component\DependencyInjection\Loader;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\ExpressionLanguage\Expression;
@@ -27,8 +28,15 @@
  *
  * @author Théo FIDRY <theo.fidry@gmail.com>
  */
-final class PsyshExtension extends Extension
+final class PsyshExtension extends Extension implements PrependExtensionInterface
 {
+    public function prepend(ContainerBuilder $container)
+    {
+        if (class_exists(TestContainer::class)) {
+            $container->prependExtensionConfig('framework', ['test' => true]);
+        }
+    }
+
     /**
      * {@inheritdoc}
      */
@@ -36,9 +44,6 @@ public function load(array $configs, ContainerBuilder $container)
     {
         $loader = new Loader\XmlFileLoader($container, new FileLocator(__DIR__.'/../../resources/config'));
         $loader->load('services.xml');
-        if (class_exists(TestContainer::class) && !$container->has('test.service_container')) {
-            $loader->load('test.xml');
-        }
 
         $configuration = new Configuration();
         $config = $this->processConfiguration($configuration, $configs);
@@ -47,7 +52,7 @@ public function load(array $configs, ContainerBuilder $container)
                 $value = new Reference(substr($value, 1));
             }
         }
-        $containerId = $container->has('test.service_container') ? 'test.service_container' : 'service_container';
+        $containerId = class_exists(TestContainer::class) ? 'test.service_container' : 'service_container';
         $container->findDefinition('psysh.shell')
             ->addMethodCall('setScopeVariables', [$config['variables'] + [
                 'container' => new Reference($containerId),
diff --git a/tests/Command/PsyshCommandIntegrationTest.php b/tests/Command/PsyshCommandIntegrationTest.php
index 0ed0ec9..d39dd53 100644
--- a/tests/Command/PsyshCommandIntegrationTest.php
+++ b/tests/Command/PsyshCommandIntegrationTest.php
@@ -63,7 +63,7 @@ public function testScopeVariables()
     public function testContainerInstance()
     {
         $container = $this->shell->getScopeVariable('container');
-        if (class_exists(TestContainer::class)) {
+        if (self::$kernel->getContainer()->has('test.service_container')) {
             $this->assertInstanceOf(TestContainer::class, $container);
         } else {
             $this->assertInstanceOf(Container::class, $container);