deleted file mode 100644
--- a/testing/web-platform/mozilla/meta/service-workers/service-worker/update.https.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[update.https.html]
-  type: testharness
-  [Update a registration]
-    expected: FAIL
-

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/mozilla/tests/service-workers/service-worker/resources/update-worker.py
@@ -0,0 +1,34 @@
+import time
+
+def main(request, response):
+    # Set mode to 'init' for initial fetch.
+    mode = 'init'
+    if 'mode' in request.cookies:
+        mode = request.cookies['mode'].value
+
+    # no-cache itself to ensure the user agent finds a new version for each update.
+    headers = [('Cache-Control', 'no-cache, must-revalidate'),
+               ('Pragma', 'no-cache')]
+
+    content_type = ''
+
+    if mode == 'init':
+        # Set a normal mimetype.
+        # Set cookie value to 'normal' so the next fetch will work in 'normal' mode.
+        content_type = 'application/javascript'
+        response.set_cookie('mode', 'normal')
+    elif mode == 'normal':
+        # Set a normal mimetype.
+        # Set cookie value to 'error' so the next fetch will work in 'error' mode.
+        content_type = 'application/javascript'
+        response.set_cookie('mode', 'error');
+    elif mode == 'error':
+        # Set a disallowed mimetype.
+        # Unset and delete cookie to clean up the test setting.
+        content_type = 'text/html'
+        response.delete_cookie('mode')
+
+    headers.append(('Content-Type', content_type))
+    # Return a different script for each access.
+    return headers, '// %s' % (time.time())
+

--- a/testing/web-platform/mozilla/tests/service-workers/service-worker/update.https.html
+++ b/testing/web-platform/mozilla/tests/service-workers/service-worker/update.https.html
@@ -4,55 +4,72 @@
 <script src="/resources/testharnessreport.js"></script>
 <script src="resources/test-helpers.sub.js"></script>
 <script>
 promise_test(function(t) {
     var scope = 'resources/scope/update';
     var worker_url = 'resources/update-worker.py';
     var expected_url = normalizeURL(worker_url);
     var registration;
-
     return service_worker_unregister_and_register(t, worker_url, scope)
       .then(function(r) {
           registration = r;
           return wait_for_state(t, registration.installing, 'activated');
         })
       .then(function() {
           assert_equals(registration.installing, null,
-                        'installing should be null in the initial state');
+                        'installing should be null in the initial state.');
           assert_equals(registration.waiting, null,
-                        'waiting should be null in the initial state');
+                        'waiting should be null in the initial state.');
           assert_equals(registration.active.scriptURL, expected_url,
-                        'active should exist in the initial state');
-
-          // A new worker should be found.
-          registration.update();
-          return wait_for_update(t, registration);
+                        'active should exist in the initial state.');
+          // A new worker (generated by update-worker.py) should be found.
+          // The returned promise should resolve when a new worker script is
+          // fetched and starts installing.
+          return Promise.all([registration.update(),
+                              wait_for_update(t, registration)]);
         })
       .then(function() {
           assert_equals(registration.installing.scriptURL, expected_url,
-                        'new installing should be set after updatefound');
+                        'new installing should be set after update resolves.');
           assert_equals(registration.waiting, null,
-                        'waiting should still be null after updatefound');
+                        'waiting should still be null after update resolves.');
           assert_equals(registration.active.scriptURL, expected_url,
-                        'active should still exist after update found');
+                        'active should still exist after update found.');
           return wait_for_state(t, registration.installing, 'installed');
         })
       .then(function() {
           assert_equals(registration.installing, null,
-                        'installing should be null after installing');
-          assert_equals(registration.waiting.scriptURL, expected_url,
-                        'waiting should be set after installing');
-          assert_equals(registration.active.scriptURL, expected_url,
-                        'active should still exist after installing');
-          return wait_for_state(t, registration.waiting, 'activated');
+                        'installing should be null after installing.');
+          if (registration.waiting) {
+            assert_equals(registration.waiting.scriptURL, expected_url,
+                          'waiting should be set after installing.');
+            assert_equals(registration.active.scriptURL, expected_url,
+                          'active should still exist after installing.');
+            return wait_for_state(t, registration.waiting, 'activated');
+          }
         })
       .then(function() {
           assert_equals(registration.installing, null,
-                        'installing should be null after activated');
+                        'installing should be null after activated.');
           assert_equals(registration.waiting, null,
-                        'waiting should be null after activated');
+                        'waiting should be null after activated.');
           assert_equals(registration.active.scriptURL, expected_url,
-                        'new worker should be promoted to active');
-          return service_worker_unregister_and_done(t, scope);
+                        'new worker should be promoted to active.');
+        })
+      .then(function() {
+          // A new worker(generated by update-worker.py) should be found.
+          // The returned promise should reject as update-worker.py sets the
+          // mimetype to a disallowed value for this attempt.
+          return registration.update();
         })
-  }, 'Update a registration');
+      .then(
+        function() { assert_unreached("update() should reject."); },
+        function(e) {
+          assert_throws('SecurityError', function() { throw e; },
+                        'Using a disallowed mimetype should make update() ' +
+                        'promise reject with a SecurityError.');
+          assert_equals(registration.active.scriptURL, expected_url,
+                        'active should still exist after update failure.');
+          return service_worker_unregister_and_done(t, scope);
+        });
+  }, 'Update a registration.');
 </script>