anchor.diff:  });
   
   class SpriteAssetProviderMock extends Mock implements SpriteAssetProvider {
  -
  +  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
   }
   
   class TransformMock extends Mock implements Transform {
  -
  +  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
   }
   
   class TestSpriteSheetEngine extends Mock implements SpriteSheetEngine {
  -
  +  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
   }
  
positive.code:       transformer = new HtmlInspector(new TestSpriteSheetEngine(), new StitchAssetProvider());
      });
  
      it("returns true for HTML assets", () {
        expect(
            transformer.isPrimary(createAsset("index.html")),
            completion(isTrue));
      });
  
      it("returns true for HTM assets", () {
        expect(
            transformer.isPrimary(createAsset("index.htm")),
            completion(isTrue));
      });
  
      it("returns false for non-HTML and non-HTM assets", () {
        expect(
            transformer.isPrimary(createAsset("index.dart")),
            completion(isFalse));
  
negative.code:     });
  
      describe("when primary input has linked stylesheets", () {
        beforeEach(() => buildTransformer(htmlWithCss));
  
        it("requests provider for assets", () {
          transformer.apply(transform).then(expectAsync((_) => provider
  