diff --git a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
index 1790a59..24bc068 100644
--- a/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
@@ -11,12 +11,41 @@
 use Drupal\Core\Ajax\AlertCommand;
 use Drupal\Core\Ajax\CloseDialogCommand;
 use Drupal\Core\Ajax\HtmlCommand;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Url;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Provides content for dialog tests.
  */
-class AjaxTestController {
+class AjaxTestController implements ContainerInjectionInterface {
+
+  /**
+   * The renderer service.
+   *
+   * @var \Drupal\Core\Render\RendererInterface
+   */
+  protected $renderer;
+
+  /**
+   * Constructs a content for dialog tests.
+   *
+   * @param \Drupal\Core\Render\RendererInterface $renderer
+   *   The renderer service.
+   */
+  public function __construct(RendererInterface $renderer) {
+    $this->renderer = $renderer;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('renderer')
+    );
+  }
 
   /**
    * Returns example content for dialog testing.
@@ -48,8 +77,7 @@ public function render() {
         ),
       ),
     );
-    // @todo Why is this being tested via an explicit drupal_render() call?
-    drupal_render($attached);
+    $this->render($attached);
     drupal_process_attached($attached);
     $response = new AjaxResponse();
     return $response;