diff --git a/core/modules/system/src/Tests/Theme/ThemeSuggestionsAlterTest.php b/core/modules/system/src/Tests/Theme/ThemeSuggestionsAlterTest.php
index 1db3583..ece21d1 100644
--- a/core/modules/system/src/Tests/Theme/ThemeSuggestionsAlterTest.php
+++ b/core/modules/system/src/Tests/Theme/ThemeSuggestionsAlterTest.php
@@ -156,6 +156,30 @@ public function testSuggestionsAlterInclude() {
     $this->assertText('Function suggested via suggestion alter hook found in include file.', 'Include file loaded for second request.');
   }
 
+
+  /**
+   * Tests hook_theme_suggestions_HOOK().
+   */
+  public function testArraySuggestions() {
+    $this->drupalGet('theme-test/array-suggestions');
+    $this->assertText('Template for testing suggestion hooks with an array of theme suggestions.');
+
+    // Enable the theme_suggestions_test module to test modules implementing
+    // suggestions hooks.
+    \Drupal::service('module_installer')->install(array('theme_suggestions_test'));
+
+    // Install test_theme to provide a template for the suggestion added in
+    // theme_suggestions_test module.
+    $this->config('system.theme')
+      ->set('default', 'test_theme')
+      ->save();
+
+    $this->resetAll();
+    $this->drupalGet('theme-test/array-suggestions');
+    $this->assertText('Template overridden based on new theme suggestion provided by a module via hook_theme_suggestions_HOOK().');
+  }
+
+
   /**
    * Tests execution order of theme suggestion alter hooks.
    *
diff --git a/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php b/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
index 4b6d528..027ae71 100644
--- a/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigDebugMarkupTest.php
@@ -24,10 +24,11 @@ class TwigDebugMarkupTest extends WebTestBase {
   public static $modules = array('theme_test', 'node');
 
   /**
-   * Tests debug markup added to Twig template output.
+   * {@inheritdoc}
    */
-  function testTwigDebugMarkup() {
-    $extension = twig_extension();
+  protected function setUp() {
+    parent::setUp();
+
     \Drupal::service('theme_handler')->install(array('test_theme'));
     $this->config('system.theme')->set('default', 'test_theme')->save();
     $this->drupalCreateContentType(array('type' => 'page'));
@@ -37,7 +38,13 @@ function testTwigDebugMarkup() {
     $this->setContainerParameter('twig.config', $parameters);
     $this->rebuildContainer();
     $this->resetAll();
+  }
 
+  /**
+   * Tests debug markup added to Twig template output.
+   */
+  function testTwigDebugMarkup() {
+    $extension = twig_extension();
     $cache = $this->container->get('theme.registry')->get();
     // Create array of Twig templates.
     $templates = drupal_find_theme_templates($cache, $extension, drupal_get_path('theme', 'test_theme'));
@@ -83,4 +90,37 @@ function testTwigDebugMarkup() {
     $this->assertFalse(strpos($output, '<!-- THEME DEBUG -->') !== FALSE, 'Twig debug markup not found in theme output when debug is disabled.');
   }
 
+  /**
+   * Tests debug markup for array suggestions and hook_theme_suggestions_HOOK().
+   */
+  public function testArraySuggestionsTwigDebugMarkup() {
+    \Drupal::service('module_installer')->install(array('theme_suggestions_test'));
+    $extension = twig_extension();
+
+    $this->drupalGet('theme-test/array-suggestions');
+    $this->assertTrue(strpos($this->getRawContent(), "THEME HOOK: 'theme_test_array_suggestions'") !== FALSE, 'Theme call information found.');
+    $this->assertTrue(strpos($this->getRawContent(), '<!-- FILE NAME SUGGESTIONS:' . PHP_EOL .  '   * theme-test-array-suggestions--not-implemented' . $extension . PHP_EOL . '   x theme-test-array-suggestions--suggestion-from-hook' . $extension . PHP_EOL . '   * theme-test-array-suggestions' . $extension . PHP_EOL . '-->') !== FALSE, 'Suggested template files found in order and correct suggestion shown as current template.');
+  }
+
+  /**
+   * Tests debug markup for specific suggestions without implementation.
+   */
+  public function testUnimplementedSpecificSuggestionsTwigDebugMarkup() {
+    $extension = twig_extension();
+    $this->drupalGet('theme-test/specific-suggestion');
+    $this->assertTrue(strpos($this->getRawContent(), "THEME HOOK: 'theme_test_specific_suggestions__not__found'") !== FALSE, 'Theme call information found.');
+    $this->assertTrue(strpos($this->getRawContent(), '<!-- FILE NAME SUGGESTIONS:' . PHP_EOL . '   * theme-test-specific-suggestions--not--found' . $extension . PHP_EOL  . '   * theme-test-specific-suggestions--not' . $extension . PHP_EOL . '   x theme-test-specific-suggestions' . $extension . PHP_EOL . '-->') !== FALSE, 'Suggested template files found in order and base template shown as current template.');
+  }
+
+
+  /**
+   * Tests debug markup for specific suggestions.
+   */
+  public function testSpecificSuggestionsTwigDebugMarkup() {
+    $extension = twig_extension();
+    $this->drupalGet('theme-test/specific-suggestion-alter');
+    $this->assertTrue(strpos($this->getRawContent(), "THEME HOOK: 'theme_test_specific_suggestions__variant'") !== FALSE, 'Theme call information found.');
+    $this->assertTrue(strpos($this->getRawContent(), '<!-- FILE NAME SUGGESTIONS:' . PHP_EOL . '   x theme-test-specific-suggestions--variant' . $extension . PHP_EOL . '   * theme-test-specific-suggestions' . $extension . PHP_EOL . '-->') !== FALSE, 'Suggested template files found in order and suggested template shown as current.');
+  }
+
 }
diff --git a/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module b/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
index 974856a..1d8cbf2 100644
--- a/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
+++ b/core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
@@ -55,3 +55,10 @@ function theme_suggestions_test_theme_suggestions_theme_test_specific_suggestion
 function theme_suggestions_test_theme_suggestions_theme_test_suggestions_include_alter(array &$suggestions, array $variables, $hook) {
   $suggestions[] = 'theme_suggestions_test_include';
 }
+
+/**
+ * Implements hook_theme_suggestions_HOOK().
+ */
+function theme_suggestions_test_theme_suggestions_theme_test_array_suggestions(array $variables) {
+  return array('theme_test_array_suggestions__suggestion_from_hook');
+}
diff --git a/core/modules/system/tests/modules/theme_test/src/ThemeTestController.php b/core/modules/system/tests/modules/theme_test/src/ThemeTestController.php
index 335ed83..d74e10c 100644
--- a/core/modules/system/tests/modules/theme_test/src/ThemeTestController.php
+++ b/core/modules/system/tests/modules/theme_test/src/ThemeTestController.php
@@ -110,6 +110,14 @@ function generalSuggestionAlter() {
     return array('#theme' => 'theme_test_general_suggestions');
   }
 
+
+  /**
+   * Menu callback for testing direct suggestions without implementation.
+   */
+  public function specificSuggestion() {
+    return array('#theme' => 'theme_test_specific_suggestions__not__found');
+  }
+
   /**
    * Menu callback for testing suggestion alter hooks with specific suggestions.
    */
@@ -133,6 +141,14 @@ function suggestionAlterInclude() {
   }
 
   /**
+   * Menu callback for testing suggestion hooks with an array of theme hooks.
+   */
+  public function arraySuggestions() {
+    return array('#theme' => array('theme_test_array_suggestions__not_implemented', 'theme_test_array_suggestions'));
+  }
+
+
+  /**
    * Controller to ensure that no theme is initialized.
    *
    * @return \Symfony\Component\HttpFoundation\JsonResponse
diff --git a/core/modules/system/tests/modules/theme_test/templates/theme-test-array-suggestions.html.twig b/core/modules/system/tests/modules/theme_test/templates/theme-test-array-suggestions.html.twig
new file mode 100644
index 0000000..bb52340
--- /dev/null
+++ b/core/modules/system/tests/modules/theme_test/templates/theme-test-array-suggestions.html.twig
@@ -0,0 +1,2 @@
+{# Output for Theme API test #}
+Template for testing suggestion hooks with an array of theme suggestions.
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 7ba5c2d..b4778d1 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -52,6 +52,9 @@ function theme_test_theme($existing, $type, $theme, $path) {
     'variables' => array(),
     'function' => 'theme_theme_test_function_template_override',
   );
+  $items['theme_test_array_suggestions'] = array(
+    'variables' => array(),
+  );
   $info['test_theme_not_existing_function'] = array(
     'function' => 'test_theme_not_existing_function',
   );
diff --git a/core/modules/system/tests/modules/theme_test/theme_test.routing.yml b/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
index 2dbd188..726734d 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
+++ b/core/modules/system/tests/modules/theme_test/theme_test.routing.yml
@@ -77,6 +77,14 @@ suggestion_provided:
     _access: 'TRUE'
 
 specific_suggestion_alter:
+  path: '/theme-test/specific-suggestion'
+  defaults:
+    _controller: '\Drupal\theme_test\ThemeTestController::specificSuggestion'
+  requirements:
+    _access: 'TRUE'
+
+    
+specific_suggestion_alter:
   path: '/theme-test/specific-suggestion-alter'
   defaults:
     _controller: '\Drupal\theme_test\ThemeTestController::specificSuggestionAlter'
@@ -97,6 +105,13 @@ suggestion_alter_include:
   requirements:
     _access: 'TRUE'
 
+theme_test.array_suggestions:
+  path: '/theme-test/array-suggestions'
+  defaults:
+    _controller: '\Drupal\theme_test\ThemeTestController::arraySuggestions'
+  requirements:
+    _access: 'TRUE'
+
 theme_test.non_html:
   path: '/theme-test/non-html'
   defaults:
diff --git a/core/modules/system/tests/themes/test_theme/templates/theme-test-array-suggestions--suggestion-from-hook.html.twig b/core/modules/system/tests/themes/test_theme/templates/theme-test-array-suggestions--suggestion-from-hook.html.twig
new file mode 100644
index 0000000..2a00d59
--- /dev/null
+++ b/core/modules/system/tests/themes/test_theme/templates/theme-test-array-suggestions--suggestion-from-hook.html.twig
@@ -0,0 +1,2 @@
+{# Output for Theme API test #}
+Template overridden based on new theme suggestion provided by a module via hook_theme_suggestions_HOOK().