diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index bf85576..645b306 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -1683,6 +1683,45 @@ class JavaScriptTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Tests adding JavaScript files with additional attributes.
+   */
+  function testAttributes() {
+    // Add internal and external JavaScript files that add the 'async' and
+    // 'defer' attributes, and check that these attributes appear on the
+    // <script> tags.
+    $js_internal = 'misc/collapse.js';
+    $js_external = 'http://example.com/script.js';
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array('attributes' => array('async' => 'async'), 'defer' => 'defer', 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async" and @defer="defer"]'), 'Rendered internal JavaScript with correct defer and async attributes.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async" and @defer="defer"]'), 'Rendered external JavaScript with correct defer and async attributes.');
+  }
+
+  /**
+   * Tests that attributes are maintained when JS aggregation is enabled.
+   */
+  function testAggregatedAttributes() {
+    // Enable aggregation.
+    variable_set('preprocess_js', TRUE);
+
+    // Add internal and external JavaScript files that add the 'async' and
+    // 'defer' attributes, and check that these attributes appear on the
+    // <script> tags.
+    $js_internal = 'misc/collapse.js';
+    $js_external = 'http://example.com/script.js';
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array('attributes' => array('async' => 'async'), 'defer' => 'defer', 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async" and @defer="defer"]'), 'Rendered internal JavaScript with correct defer and async attributes.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async" and @defer="defer"]'), 'Rendered external JavaScript with correct defer and async attributes.');
+  }
+
+  /**
    * Test altering a JavaScript's weight via hook_js_alter().
    *
    * @see simpletest_js_alter()