Add test that actually tests the test

python/tidy/servo_tidy_tests/manifest-include.ini

@@ -1,109 +1,5 @@
 skip: true
-[_mozilla]
-  skip: false
-[2dcontext]
-  skip: false
-[cors]
-  skip: false
-[css]
-  skip: true
-  [compositing]
-    skip: false
-  [CSS2]
-    skip: false
-  [css-animations]
-    skip: false
-  [css-backgrounds]
-    skip: false
-  [css-color]
-    skip: false
-  [css-conditional]
-    skip: false
-  [css-flexbox]
-    skip: false
-  [css-images]
-    skip: false
-  [css-style-attr]
-    skip: false
-  [css-text]
-    skip: false
-  [css-text-decor]
-    skip: false
-  [css-transforms]
-    skip: false
-  [css-transitions]
-    skip: false
-  [css-ui]
-    skip: false
-  [css-values]
-    skip: false
-  [css-variables]
-    skip: false
-  [cssom]
-    skip: false
-  [cssom-view]
-    skip: false
-  [filter-effects]
-    skip: false
-  [geometry]
-    skip: false
-  [mediaqueries]
-    skip: false
-  [selectors]
-    skip: false
-[custom-elements]
-  skip: false
-[dom]
-  skip: false
-[domparsing]
-  skip: false
-[encoding]
-  skip: false
-[eventsource]
-  skip: false
-[fetch]
-  skip: false
-[FileAPI]
-  skip: false
-[fullscreen]
-  skip: false
-[hr-time]
-  skip: false
 [html]
   skip: false
-[js]
-  skip: false
-[navigation-timing]
-  skip: false
-[old-tests]
-  skip: true
-  [submission]
-    skip: true
-[performance-timeline]
-  skip: false
-[quirks]
-  skip: false
-[referrer-policy]
-  skip: false
-[subresource-integrity]
-  skip: false
-[touch-events]
-  skip: false
-[uievents]
-  skip: false
-[url]
-  skip: false
-[WebCryptoAPI]
-  skip: false
-[webgl]
-  skip: false
-[WebIDL]
-  skip: false
-[websockets]
-  skip: false
-[webstorage]
-  skip: false
-[workers]
-  skip: false
-[xhr]
+[never_going_to_exist]
   skip: false

python/tidy/servo_tidy_tests/test_tidy.py

@@ -39,6 +39,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual("%s manifest file is required but was not found" % wrong_path, errors.next()[2])
         self.assertNoMoreErrors(errors)
         errors = tidy.check_manifest_dirs(os.path.join(base_path, 'manifest-include.ini'), print_text=False)
+        self.assertTrue(errors.next()[2].endswith("never_going_to_exist"))
         self.assertNoMoreErrors(errors)
 
     def test_directory_checks(self):