diff --git a/core/modules/system/lib/Drupal/system/Tests/Bootstrap/GetFilenameUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Bootstrap/GetFilenameUnitTest.php
index 27ea1d7..a4763b6 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Bootstrap/GetFilenameUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Bootstrap/GetFilenameUnitTest.php
@@ -17,7 +17,7 @@ class GetFilenameUnitTest extends UnitTestBase {
   public static function getInfo() {
     return array(
       'name' => 'Get filename test',
-      'description' => 'Test that drupal_get_filename() works correctly when the file is not found in the database.',
+      'description' => 'Test that drupal_get_filename() works correctly.',
       'group' => 'Bootstrap',
     );
   }
@@ -50,5 +50,8 @@ function testDrupalGetFilename() {
     // will automatically check there for 'script' files, just as it does
     // for (e.g.) 'module' files in core/modules.
     $this->assertIdentical(drupal_get_filename('script', 'test'), 'core/scripts/test/test.script');
+
+    // Searching for an item that does not exist returns NULL.
+    $this->assertNull(drupal_get_filename('module', uniqid("", TRUE)), 'Searching for an item that does not exist returns NULL.');
   }
 }
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 eeb49cc..edee856 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/UrlTest.php
@@ -72,6 +72,16 @@ function testLCustomClass() {
   }
 
   /**
+   * Tests for custom class passed as string in l() function.
+   */
+  function testLCustomClassAsString() {
+    $class = $this->randomName();
+    $link = l($this->randomName(), current_path(), array('attributes' => array('class' => $class)));
+    $this->assertTrue($this->hasClass($link, $class), format_string('Custom class @class, passed as a string, is present on link when requested', array('@class' => $class)));
+  }
+
+
+  /**
    * Checks for class existence in link.
    *
    * @param $link