diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php
index 9c2105a..1fa595c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php
@@ -34,7 +34,7 @@ public static function getInfo() {
    */
   function testTwigDebugMarkup() {
     $extension = twig_extension();
-    theme_enable(array('test_theme'));
+    \Drupal::service('theme_handler')->enable(array('test_theme'));
     \Drupal::config('system.theme')->set('default', 'test_theme')->save();
     // Enable debug, rebuild the service container, and clear all caches.
     $this->settingsSet('twig_debug', TRUE);
@@ -48,7 +48,8 @@ function testTwigDebugMarkup() {
 
     // Create a node and test different features of the debug markup.
     $node = $this->drupalCreateNode();
-    $output = _theme('node', node_view($node));
+    $node_output = entity_view($node, 'full');
+    $output = drupal_render($node_output);
     $this->assertTrue(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup found in theme output when debug is enabled.');
     $this->assertTrue(strpos($output, "CALL: _theme('node')") !== FALSE, 'Theme call information found.');
     $this->assertTrue(strpos($output, 'x node--1' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   * node' . $extension) !== FALSE, 'Suggested template files found in order and node ID specific template shown as current template.');
@@ -58,14 +59,15 @@ function testTwigDebugMarkup() {
     // Create another node and make sure the template suggestions shown in the
     // debug markup are correct.
     $node2 = $this->drupalCreateNode();
-    $output = _theme('node', node_view($node2));
+    $node2_output = entity_view($node2, 'full');
+    $output = drupal_render($node2_output);
     $this->assertTrue(strpos($output, '* node--2' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   x node' . $extension) !== FALSE, 'Suggested template files found in order and base template shown as current template.');
 
     // Create another node and make sure the template suggestions shown in the
     // debug markup are correct.
     $node3 = $this->drupalCreateNode();
     $build = array('#theme' => 'node__foo__bar');
-    $build += node_view($node3);
+    $build += entity_view($node3, 'full');;
     $output = drupal_render($build);
     $this->assertTrue(strpos($output, "CALL: _theme('node__foo__bar')") !== FALSE, 'Theme call information found.');
     $this->assertTrue(strpos($output, '* node--foo--bar' . $extension . PHP_EOL . '   * node--foo' . $extension . PHP_EOL . '   * node--3' . $extension . PHP_EOL . '   * node--page' . $extension . PHP_EOL . '   x node' . $extension) !== FALSE, 'Suggested template files found in order and base template shown as current template.');
@@ -75,7 +77,8 @@ function testTwigDebugMarkup() {
     $this->rebuildContainer();
     $this->resetAll();
 
-    $output = _theme('node', node_view($node));
+    $node_output = entity_view($node, 'full');
+    $output = drupal_render($node_output);
     $this->assertFalse(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup not found in theme output when debug is disabled.');
   }
 
diff --git a/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/ThemeTestController.php b/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/ThemeTestController.php
index 31b25a0..1bfa5f8 100644
--- a/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/ThemeTestController.php
+++ b/core/modules/system/tests/modules/theme_test/lib/Drupal/theme_test/ThemeTestController.php
@@ -55,7 +55,9 @@ public function testInfoStylesheets() {
    *   A render array containing a theme override.
    */
   public function testTemplate() {
-    return _theme('theme_test_template_test');
+    return array(
+      '#theme' => 'theme_test_template_test',
+    );
   }
 
   /**
@@ -65,7 +67,9 @@ public function testTemplate() {
    *   An HTML string containing the themed output.
    */
   public function testSuggestion() {
-    return _theme(array('theme_test__suggestion', 'theme_test'), array());
+    return array(
+      '#theme' => array('theme_test__suggestion', 'theme_test'),
+    );
   }
 
 /**
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 ba2a718..b4817f5 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
@@ -16,7 +16,8 @@ class TwigThemeTestController {
    * Menu callback for testing PHP variables in a Twig template.
    */
   public function phpVariablesRender() {
-    return _theme('twig_theme_test_php_variables');
+    $twig_theme_test_php_variables = array('#theme' => 'twig_theme_test_php_variables');
+    return drupal_render($twig_theme_test_php_variables);
   }
 
   /**