diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index 2d84114..40a78f3 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -9,11 +9,9 @@ function theme_test_theme($existing, $type, $theme, $path) {
     'variables' => array('foo' => ''),
   );
   $items['theme_test_template_test'] = array(
-    'variables' => array(),
     'template' => 'theme_test.template_test',
   );
   $items['theme_test_template_test_2'] = array(
-    'variables' => array(),
     'template' => 'theme_test.template_test',
   );
   $items['theme_test_foo'] = array(
@@ -102,8 +100,7 @@ function theme_test_request_listener_page_callback() {
  * Menu callback for testing template overridding based on filename.
  */
 function theme_test_template_test_page_callback() {
-  $theme_test_template_test = array('#theme' => 'theme_test_template_test');
-  return drupal_render($theme_test_template_test);
+  return theme('theme_test_template_test');
 }
 
 /**
@@ -149,8 +146,7 @@ function _theme_test_alter() {
  * Page callback, calls a theme hook suggestion.
  */
 function _theme_test_suggestion() {
-  $theme_test = array('#theme' => array('theme_test__suggestion', 'theme_test'));
-  return drupal_render($theme_test);
+  return theme(array('theme_test__suggestion', 'theme_test'), array());
 }
 
 /**
diff --git a/core/modules/system/tests/modules/twig_theme_test/lib/Drupal/twig_theme_test/TwigThemeTestController.php b/core/modules/system/tests/modules/twig_theme_test/lib/Drupal/twig_theme_test/TwigThemeTestController.php
index e873956..9179de9 100644
--- a/core/modules/system/tests/modules/twig_theme_test/lib/Drupal/twig_theme_test/TwigThemeTestController.php
+++ b/core/modules/system/tests/modules/twig_theme_test/lib/Drupal/twig_theme_test/TwigThemeTestController.php
@@ -26,8 +26,7 @@ public static function create(ContainerInterface $container) {
    * Menu callback for testing PHP variables in a Twig template.
    */
   public function phpVariablesRender() {
-    $twig_theme_test_php_variables = array('#theme' => 'twig_theme_test_php_variables');
-    return drupal_render($twig_theme_test_php_variables);
+    return theme('twig_theme_test_php_variables');
   }
 
   /**
diff --git a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
index cc74184..934d1b0 100644
--- a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
+++ b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
@@ -5,7 +5,6 @@
  */
 function twig_theme_test_theme($existing, $type, $theme, $path) {
   $items['twig_theme_test_php_variables'] = array(
-    'variables' => array(),
     'template' => 'twig_theme_test.php_variables',
   );
   $items['twig_theme_test_trans'] = array(