diff --git a/core/modules/system/tests/modules/ajax_test/ajax_test.module b/core/modules/system/tests/modules/ajax_test/ajax_test.module
deleted file mode 100644
index de741fe..0000000
--- a/core/modules/system/tests/modules/ajax_test/ajax_test.module
+++ /dev/null
@@ -1,40 +0,0 @@
-<?php
-
-/**
- * @file
- * Helper module for Ajax framework tests.
- */
-
-use Drupal\Core\Ajax\AjaxResponse;
-use Drupal\Core\Ajax\AlertCommand;
-use Drupal\Core\Ajax\OpenDialogCommand;
-use Drupal\Core\Ajax\OpenModalDialogCommand;
-use Drupal\Core\Ajax\CloseDialogCommand;
-use Drupal\Core\Url;
-
-/**
- * Menu callback: Returns AJAX element with #error property set.
- *
- * @deprecated \Drupal\ajax_test\Controller\AjaxTestController::renderError()
- */
-function ajax_test_error() {
-  $message = '';
-  $query = \Drupal::request()->query;
-  if ($query->has('message')) {
-    $message = $query->get('message');
-  }
-  $response = new AjaxResponse();
-  $response->addCommand(new AlertCommand($message));
-  return $response;
-}
-
-/**
- * Menu callback: Close the ajax dialog.
- *
- * @deprecated \Drupal\ajax_test\Controller\AjaxTestController::dialogClose()
- */
-function ajax_test_dialog_close() {
-  $response = new AjaxResponse();
-  $response->addCommand(new CloseDialogCommand('#ajax-test-dialog-wrapper-1'));
-  return $response;
-}
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 928b84e..9279b0d 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
@@ -8,8 +8,11 @@
 namespace Drupal\ajax_test\Controller;
 
 use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\AlertCommand;
+use Drupal\Core\Ajax\CloseDialogCommand;
 use Drupal\Core\Ajax\HtmlCommand;
 use Drupal\Core\Url;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Provides content for dialog tests.
@@ -80,14 +83,27 @@ public function order() {
   }
 
   /**
-   * @todo Remove ajax_test_error().
+   * Menu callback: Returns AJAX element with #error property set.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The current request object.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse
+   *   The JSON response object.
    */
-  public function renderError() {
-    return ajax_test_error();
+  public function renderError(Request $request) {
+    $message = '';
+    $query = $request->query;
+    if ($query->has('message')) {
+      $message = $query->get('message');
+    }
+    $response = new AjaxResponse();
+    $response->addCommand(new AlertCommand($message));
+    return $response;
   }
 
   /**
-   * @todo Remove ajax_test_dialog().
+   * Menu callback: Renders a form elements and links with #ajax['dialog'].
    */
   public function dialog() {
     // Add two wrapper elements for testing non-modal dialogs. Modal dialogs use
@@ -180,10 +196,15 @@ public function dialog() {
   }
 
   /**
-   * @todo Remove ajax_test_dialog_close().
+   * Close the ajax dialog.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse $response
+   *   The JSON response object.
    */
   public function dialogClose() {
-    return ajax_test_dialog_close();
+    $response = new AjaxResponse();
+    $response->addCommand(new CloseDialogCommand('#ajax-test-dialog-wrapper-1'));
+    return $response;
   }
 
 }