diff --git a/core/modules/system/tests/modules/form_test/form_test.module b/core/modules/system/tests/modules/form_test/form_test.module
index a3d1cd0..bf8b101 100644
--- a/core/modules/system/tests/modules/form_test/form_test.module
+++ b/core/modules/system/tests/modules/form_test/form_test.module
@@ -2057,34 +2057,6 @@ function form_test_required_attribute($form, &$form_state) {
 }
 
 /**
- * Menu callback returns two instances of the same form.
- *
- * @deprecated \Drupal\form_test\Controller\FormTestController::doubleForm()
- */
-function form_test_double_form() {
-  return array(
-    'form1' => drupal_get_form('form_test_html_id'),
-    'form2' => drupal_get_form('form_test_html_id'),
-  );
-}
-
-/**
- * Builds a simple form to test duplicate HTML IDs.
- */
-function form_test_html_id($form, &$form_state) {
-  $form['name'] = array(
-    '#type' => 'textfield',
-    '#title' => 'name',
-    '#required' => TRUE,
-  );
-  $form['submit'] = array(
-    '#type' => 'submit',
-    '#value' => 'Save',
-  );
-  return $form;
-}
-
-/**
  * Builds a simple form to test form button classes.
  *
  * @deprecated Use \Drupal\form_test\testButtonClass()
diff --git a/core/modules/system/tests/modules/form_test/form_test.routing.yml b/core/modules/system/tests/modules/form_test/form_test.routing.yml
index f8467ff..26eab9c 100644
--- a/core/modules/system/tests/modules/form_test/form_test.routing.yml
+++ b/core/modules/system/tests/modules/form_test/form_test.routing.yml
@@ -81,7 +81,7 @@ form_test.double_form:
   path: '/form-test/double-form'
   defaults:
     _title: 'Double form test'
-    _content: '\Drupal\form_test\Controller\FormTestController::doubleForm'
+    _content: '\Drupal\form_test\Controller\FormTestController::twoIdenticalFormInstances'
   requirements:
     _access: 'TRUE'
 
diff --git a/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Controller/FormTestController.php b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Controller/FormTestController.php
index 40dd178..f9bf52c 100644
--- a/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Controller/FormTestController.php
+++ b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Controller/FormTestController.php
@@ -8,6 +8,7 @@
 
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\Language\Language;
+use Drupal\form_test\Form\FormTestHtmlIdForm;
 
 /**
  * Controller routines for form_test routes.
@@ -43,10 +44,16 @@ public function wrapperCallback($form_id) {
   }
 
   /**
-   * @todo Remove form_test_double_form().
+   * Returns two instances of the same form.
+   *
+   * @return array
+   *   A render array containing two identical forms.
    */
-  public function doubleForm() {
-    return form_test_double_form();
+  public function twoIdenticalFormInstances() {
+    return array(
+      'form1' => drupal_get_form(new FormTestHtmlIdForm()),
+      'form2' => drupal_get_form(new FormTestHtmlIdForm()),
+    );
   }
 
 }
diff --git a/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Form/FormTestHtmlIdForm.php b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Form/FormTestHtmlIdForm.php
new file mode 100644
index 0000000..a1bcdd8
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/Form/FormTestHtmlIdForm.php
@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestHtmlIdForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Provides a simple form to test duplicate HTML IDs.
+ */
+class FormTestHtmlIdForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormID() {
+    return 'form_test_html_id';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    $form['name'] = array(
+      '#type' => 'textfield',
+      '#title' => 'name',
+      '#required' => TRUE,
+    );
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => 'Save',
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}