pkg/unittest: test cleanup

pkg/unittest/test/missing_tick_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+library unittest.missing_tick_test;
+
 import 'package:unittest/unittest.dart';
 
 // TODO(gram): Convert to a shouldFail passing test.
-main() {
+void main() {
   SimpleConfiguration config = unittestConfiguration;
   config.timeout = const Duration(seconds: 2);
   group('Broken', () {
     test('test that should time out', () {
       expectAsync(() {});
     });
   });
 }