diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
index ac834d1..3a108af 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageSwitchingTest.php
@@ -19,7 +19,7 @@ class LanguageSwitchingTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = array('language', 'block');
+  public static $modules = array('language', 'block', 'language_test');
 
   public static function getInfo() {
     return array(
@@ -89,4 +89,101 @@ function testLanguageBlock() {
     $this->assertIdentical($anchors, array('active' => array('en'), 'inactive' => array('fr')), 'Only the current language anchor is marked as active on the language switcher block.');
   }
 
+  /**
+   * Test active class on links when switching language.
+   */
+  function testLinkLanguageSwitchingActiveClass() {
+    // Add language.
+    $edit = array(
+      'predefined_langcode' => 'fr',
+    );
+    $this->drupalPost('admin/config/regional/language/add', $edit, t('Add language'));
+
+    // Enable URL language detection and selection.
+    $edit = array('language_interface[enabled][language-url]' => '1');
+    $this->drupalPost('admin/config/regional/language/detection', $edit, t('Save settings'));
+
+    // Test l().
+    $function_name = 'l()';
+
+    // Test URLs on an English page.
+    $current_language = 'English';
+    $this->drupalGet('language_test/l-active-class');
+
+    // No lang link should be active.
+    $langcode = 'none';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // en link should be active.
+    $langcode = 'en';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'en_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // fr link should NOT be active.
+    $langcode = 'fr';
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'fr_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // Test URLs on a French page.
+    $current_language = 'French';
+    $this->drupalGet('fr/language_test/l-active-class');
+
+    // No lang link should be active.
+    $langcode = 'none';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // en link should NOT be active.
+    $langcode = 'en';
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'en_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // fr link should be active.
+    $langcode = 'fr';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'fr_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // Test theme('link').
+    $function_name = "theme('link')";
+
+    // Test URLs on an English page.
+    $current_language = 'English';
+    $this->drupalGet('language_test/theme-link-active-class');
+
+    // No lang link should be active.
+    $langcode = 'none';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // en link should be active.
+    $langcode = 'en';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'en_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // fr link should NOT be active.
+    $langcode = 'fr';
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'fr_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // Test URLs on a French page.
+    $current_language = 'French';
+    $this->drupalGet('fr/language_test/theme-link-active-class');
+
+    // No lang link should be active.
+    $langcode = 'none';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'no_lang_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // en link should NOT be active.
+    $langcode = 'en';
+    $links = $this->xpath('//a[@id = :id and not(contains(@class, :class))]', array(':id' => 'en_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is NOT marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+
+    // fr link should be active.
+    $langcode = 'fr';
+    $links = $this->xpath('//a[@id = :id and contains(@class, :class)]', array(':id' => 'fr_link', ':class' => 'active'));
+    $this->assertTrue(isset($links[0]), t('A link generated by :function to the current :language page with langcode :langcode is marked active.', array(':function' => $function_name, ':language' => $current_language, ':langcode' => $langcode)));
+  }
+
 }
diff --git a/core/modules/language/tests/language_test/language_test.module b/core/modules/language/tests/language_test/language_test.module
index cb97937..43457df 100644
--- a/core/modules/language/tests/language_test/language_test.module
+++ b/core/modules/language/tests/language_test/language_test.module
@@ -109,6 +109,16 @@ function language_test_menu() {
     'access callback' => TRUE,
     'type' => MENU_CALLBACK,
   );
+  $items['language_test/l-active-class'] = array(
+    'page callback' => 'language_test_l_active_class',
+    'access callback' => TRUE,
+    'type' => MENU_CALLBACK,
+  );
+  $items['language_test/theme-link-active-class'] = array(
+    'page callback' => 'language_test_theme_link_active_class',
+    'access callback' => TRUE,
+    'type' => MENU_CALLBACK,
+  );
 
   return $items;
 }
@@ -119,3 +129,89 @@ function language_test_menu() {
 function language_test_subrequest() {
   return drupal_container()->get('http_kernel')->handle(Request::create('/user'), HttpKernelInterface::SUB_REQUEST);
 }
+
+/**
+ * Page callback: Displays links to the current page, with different langcodes.
+ *
+ * Using #theme causes these links to be rendered with theme_link().
+ */
+function language_test_theme_link_active_class() {
+  $languages = language_list();
+  return array(
+    'no_language' => array(
+      '#theme' => 'link',
+      '#text' => t('Link to the current path with no langcode provided.'),
+      '#path' => current_path(),
+      '#options' => array(
+        'attributes' => array(
+          'id' => array('no_lang_link'),
+        ),
+      ),
+    ),
+    'fr' => array(
+      '#theme' => 'link',
+      '#text' => t('Link to a French version of the current path.'),
+      '#path' => current_path(),
+      '#options' => array(
+        'language' => $languages['fr'],
+        'attributes' => array(
+          'id' => array('fr_link'),
+        ),
+      ),
+    ),
+    'en' => array(
+      '#theme' => 'link',
+      '#text' => t('Link to an English version of the current path.'),
+      '#path' => current_path(),
+      '#options' => array(
+        'language' => $languages['en'],
+        'attributes' => array(
+          'id' => array('en_link'),
+        ),
+      ),
+    ),
+  );
+}
+
+/**
+ * Page callback: Displays links to the current page, with different langcodes.
+ *
+ * Using #type causes these links to be rendered with l().
+ */
+function language_test_l_active_class() {
+  $languages = language_list();
+  return array(
+    'no_language' => array(
+      '#type' => 'link',
+      '#title' => t('Link to the current path with no langcode provided.'),
+      '#href' => current_path(),
+      '#options' => array(
+        'attributes' => array(
+          'id' => array('no_lang_link'),
+        ),
+      ),
+    ),
+    'fr' => array(
+      '#type' => 'link',
+      '#title' => t('Link to a French version of the current path.'),
+      '#href' => current_path(),
+      '#options' => array(
+        'language' => $languages['fr'],
+        'attributes' => array(
+          'id' => array('fr_link'),
+        ),
+      ),
+    ),
+    'en' => array(
+      '#type' => 'link',
+      '#title' => t('Link to an English version of the current path.'),
+      '#href' => current_path(),
+      '#options' => array(
+        'language' => $languages['en'],
+        'attributes' => array(
+          'id' => array('en_link'),
+        ),
+      ),
+    ),
+  );
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php
index 72f8af4..1a3fa14 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php
@@ -28,18 +28,29 @@ public static function getInfo() {
   }
 
   /**
-   * Confirms that invalid URLs are filtered.
+   * Confirms that invalid URLs are filtered in link generating functions.
    */
-  function testLXSS() {
+  function testLinkXSS() {
+    // Test l().
     $text = $this->randomName();
     $path = "<SCRIPT>alert('XSS')</SCRIPT>";
     $link = l($text, $path);
     $sanitized_path = check_url(url($path));
-    $this->assertTrue(strpos($link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered', array('@path' => $path)));
+    $this->assertTrue(strpos($link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered by l().', array('@path' => $path)));
+
+    // Test #theme.
+    $link_array =  array(
+      '#theme' => 'link',
+      '#text' => $this->randomName(),
+      '#path' => $path,
+    );
+    $theme_link = render($link_array);
+    $sanitized_path = check_url(url($path));
+    $this->assertTrue(strpos($theme_link, $sanitized_path) !== FALSE, format_string('XSS attack @path was filtered by #theme', array('@path' => $path)));
   }
 
   /**
-   * Tests for active class in l() function.
+   * Tests for active class in l() and '#theme' => 'link' rendarable arrays.
    */
   function testLinkActiveClass() {
     $options_no_query = array();
@@ -66,34 +77,50 @@ function testLinkActiveClass() {
     $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => url($path, $options_no_query), ':class' => 'active'));
     $this->assertTrue(isset($links[0]), 'A link generated by l() to the current page without a query string when the current page has a query string is not marked active.');
 
-    // Test theme('link').
+    // Test #theme.
     $path = 'common-test/theme-link-active-class';
 
     $this->drupalGet($path, $options_no_query);
     $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_no_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by theme(\'link\') to the current page is marked active.');
+    $this->assertTrue(isset($links[0]), 'A link generated by #theme to the current page is marked active.');
 
     $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => url($path, $options_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by theme(\'link\') to the current page with a query string when the current page has no query string is not marked active.');
+    $this->assertTrue(isset($links[0]), 'A link generated by #theme to the current page with a query string when the current page has no query string is not marked active.');
 
     $this->drupalGet($path, $options_query);
     $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by theme(\'link\') to the current page with a query string that matches the current query string is marked active.');
+    $this->assertTrue(isset($links[0]), 'A link generated by #theme to the current page with a query string that matches the current query string is marked active.');
 
     $links = $this->xpath('//a[@href = :href and contains(@class, :class)]', array(':href' => url($path, $options_query_reverse), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by theme(\'link\') to the current page with a query string that has matching parameters to the current query string but in a different order is marked active.');
+    $this->assertTrue(isset($links[0]), 'A link generated by #theme to the current page with a query string that has matching parameters to the current query string but in a different order is marked active.');
 
     $links = $this->xpath('//a[@href = :href and not(contains(@class, :class))]', array(':href' => url($path, $options_no_query), ':class' => 'active'));
-    $this->assertTrue(isset($links[0]), 'A link generated by theme(\'link\') to the current page without a query string when the current page has a query string is not marked active.');
+    $this->assertTrue(isset($links[0]), 'A link generated by #theme to the current page without a query string when the current page has a query string is not marked active.');
   }
 
   /**
-   * Tests for custom class in l() function.
+   * Tests for custom class in l() and '#theme' => 'link' renderable arrays.
    */
-  function testLCustomClass() {
-    $class = $this->randomName();
-    $link = l($this->randomName(), current_path(), array('attributes' => array('class' => array($class))));
-    $this->assertTrue($this->hasClass($link, $class), format_string('Custom class @class is present on link when requested', array('@class' => $class)));
+  function testLinkCustomClass() {
+    // Test l().
+    $class_l = $this->randomName();
+    $link_l = l($this->randomName(), current_path(), array('attributes' => array('class' => array($class_l))));
+    $this->assertTrue($this->hasClass($link_l, $class_l), format_string('Custom class @class is present on link when requested by l()', array('@class' => $class_l)));
+
+    // Test #theme.
+    $class_theme = $this->randomName();
+    $theme_link = array(
+      '#theme' => 'link',
+      '#text' => $this->randomName(),
+      '#path' => current_path(),
+      '#options' => array(
+        'attributes' => array(
+          'class' => array($class_theme),
+        ),
+      ),
+    );
+    $link_theme = render($theme_link);
+    $this->assertTrue($this->hasClass($link_theme, $class_theme), format_string('Custom class @class is present on link when requested by #theme', array('@class' => $class_theme)));
   }
 
   /**