anchor.diff:    InMemoryRunnerAssetReader reader;
     InMemoryRunnerAssetWriter writer;
     StreamSubscription subscription;
  -  Completer<Null> nextBuild;
  +  Completer<BuildResult> nextBuild;
   
     final path = p.absolute('example');
   
  
positive.code:     FakeWatcher.notifyWatchers(
        new WatchEvent(ChangeType.ADD, '$path/web/new.txt'),
      );
      await nextBuild.future;
      final response = await handler(new Request('GET', getNew));
      expect(await response.readAsString(), 'NEW');
    }, skip: 'Enable on fix of https://github.com/dart-lang/build/issues/500');
  }
  
  class UppercaseBuilder implements Builder {
  
negative.code:     ));
      handler = server.handlerFor('web');
  
      nextBuild = new Completer<BuildResult>();
      subscription = server.buildResults.listen((result) {
        nextBuild.complete(result);
        nextBuild = new Completer<BuildResult>();
      });
      await nextBuild.future;
    });
  