diff --git a/core/modules/system/src/Tests/Theme/EngineTwigTest.php b/core/modules/system/src/Tests/Theme/EngineTwigTest.php
index c03f16b..39ef521 100644
--- a/core/modules/system/src/Tests/Theme/EngineTwigTest.php
+++ b/core/modules/system/src/Tests/Theme/EngineTwigTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\system\Tests\Theme;
 
+use Drupal\Core\Url;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -63,4 +64,24 @@ public function testTwigUrlGenerator() {
     }
   }
 
+  /**
+   * Tests the link_generator twig functions.
+   */
+  public function testTwigLinkGenerator() {
+    $this->drupalGet('twig-theme-test/link-generator');
+
+    $link_generator = $this->container->get('link_generator');
+
+    $expected = [
+      'link via the linkgenerator: ' . $link_generator->generateFromUrl('register', new Url('user.register')),
+    ];
+
+    $content = $this->drupalGetContent();
+    debug($content);
+    $this->assertFalse(empty($content), 'Page content is not empty');
+    foreach ($expected as $string) {
+      $this->assertRaw('<div>' . $string . '</div>');
+    }
+  }
+
 }
diff --git a/core/modules/system/templates/menu.html.twig b/core/modules/system/templates/menu.html.twig
index 3151454..528f9d7 100644
--- a/core/modules/system/templates/menu.html.twig
+++ b/core/modules/system/templates/menu.html.twig
@@ -26,11 +26,11 @@
 {% macro menu_links(items, menu_level) %}
   {% import _self as menus %}
   {% if items %}
-    {% if menu_level is 0 %}
-      <ul {{ attributes.addClass('menu') }}>
+    {% if menu_level == 0 %}
+      <ul{{ attributes.addClass('menu') }}>
     {% else %}
       <ul class="menu">
-    {%  endif %}
+    {% endif %}
       {% for item in items %}
         <li{{ item.attributes }}>
           {{ link_from_url(item.title, item.url) }}
diff --git a/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php b/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
index d454e5f..0aed984 100644
--- a/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
+++ b/core/modules/system/tests/modules/twig_theme_test/src/TwigThemeTestController.php
@@ -6,6 +6,7 @@
  */
 
 namespace Drupal\twig_theme_test;
+use Drupal\Core\Url;
 
 /**
  * Controller routines for Twig theme test routes.
@@ -37,4 +38,14 @@ public function urlGeneratorRender() {
     );
   }
 
+  /**
+   * Renders for testing link_generator functions in a Twig template.
+   */
+  public function linkGeneratorRender() {
+    return array(
+      '#theme' => 'twig_theme_test_link_generator',
+      '#test_url' => new Url('user.register')
+    );
+  }
+
 }
diff --git a/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.link_generator.html.twig b/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.link_generator.html.twig
index e69de29..e5bf772 100644
--- a/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.link_generator.html.twig
+++ b/core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.link_generator.html.twig
@@ -0,0 +1 @@
+<div>link via the linkgenerator: {{ link_from_url("register", test_url) }}</div>
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 c8db9d6..f023cb1 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
@@ -31,6 +31,10 @@ function twig_theme_test_theme($existing, $type, $theme, $path) {
     'variables' => array(),
     'template' => 'twig_theme_test.url_generator',
   );
+  $items['twig_theme_test_link_generator'] = array(
+    'variables' => array('test_url' => NULL),
+    'template' => 'twig_theme_test.link_generator',
+  );
   return $items;
 }
 
diff --git a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
index 75b9bbb..d631898 100644
--- a/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
+++ b/core/modules/system/tests/modules/twig_theme_test/twig_theme_test.routing.yml
@@ -18,3 +18,10 @@ twig_theme_test_url_generator:
     _content: '\Drupal\twig_theme_test\TwigThemeTestController::urlGeneratorRender'
   requirements:
     _access: 'TRUE'
+
+twig_theme_test_link_generator:
+  path: '/twig-theme-test/link-generator'
+  defaults:
+    _content: '\Drupal\twig_theme_test\TwigThemeTestController::linkGeneratorRender'
+  requirements:
+    _access: 'TRUE'