anchor.diff:        transformer = new HtmlInspector(new TestSpriteSheetEngine(), new StitchAssetProvider());
       });
   
  -    it("returns true for HTML assets", () {
  +    it("completes with true for HTML assets", () {
         expect(
             transformer.isPrimary(createAsset("index.html")),
             completion(isTrue));
       });
   
  -    it("returns true for HTM assets", () {
  +    it("completes with true for HTM assets", () {
         expect(
             transformer.isPrimary(createAsset("index.htm")),
             completion(isTrue));
       });
   
  -    it("returns false for non-HTML and non-HTM assets", () {
  +    it("completes with false for non-HTML and non-HTM assets", () {
         expect(
             transformer.isPrimary(createAsset("index.dart")),
             completion(isFalse));
  
positive.code:     });
  
      describe("when provider returns list of assets", () {
        beforeEach(() => buildTransformer(htmlWithCss,
            [createAsset("images/icons/info.png"), createAsset("images/icons/star.png")],
            new SpriteSheet("spritesheet", [
              new Sprite("info.png", new Image(100, 100), new Point(0, 0)),
              new Sprite("star.png", new Image(100, 100), new Point(0, 100))
            ])));
  
negative.code:     Mock primaryInput;
      SpriteAssetProviderMock provider;
  
      void buildTransformer(String html, {List<Asset> assets: const [], SpriteSheet spriteSheet}) {
        primaryInput.when(callsTo("readAsString")).alwaysReturn(new Future.value(html));
        var spriteSheetEngine = new TestSpriteSheetEngine()
            ..when(callsTo("generate")).alwaysReturn(new Future.value(spriteSheet));
  