diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php
new file mode 100644
index 0000000..98707a5
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigDebugMarkupTest.php
@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Theme\TwigDebugMarkupTest.
+ */
+
+namespace Drupal\system\Tests\Theme;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests for Twig debug markup.
+ */
+class TwigDebugMarkupTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('theme_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Twig debug markup',
+      'description' => 'Tests Twig debug markup.',
+      'group' => 'Theme',
+    );
+  }
+
+  /**
+   * Tests that debug markup is added to Twig template output.
+   */
+  function testTwigDebugMarkup() {
+    theme_enable(array('test_theme_twig'));
+    variable_set('theme_default', 'test_theme_twig');
+    // Enable debug, rebuild the service container, and clear all caches.
+    $this->settingsSet('twig_debug', TRUE);
+    $this->rebuildContainer();
+    $this->resetAll();
+
+    $output = theme('theme_test_template_test');
+    $this->assertTrue(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup found in theme output when debug is enabled.');
+
+    // Disable debug, rebuild the service container, and clear all caches.
+    $this->settingsSet('twig_debug', FALSE);
+    $this->rebuildContainer();
+    $this->resetAll();
+
+    $output = theme('theme_test_template_test');
+    $this->assertFalse(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup not found in theme output when debug is disabled.');
+  }
+
+}