anchor.diff:  ///
   ///       test('should render "Hello World", () async {
   ///         fixture = await bed.create();
  -///         expect(fixture.rootElement, containsText('Hello World'));
  +///         expect(fixture.text, contains('Hello World'));
   ///       });
   ///
   ///       test('should render "Hello World" in all-caps', () async {
  
positive.code: ///       test('should render "Hello World", () async {
  ///         var bed = new NgTestBed<HelloWorldComponent>();
  ///         var fixture = await bed.create();
  ///         expect(controller, containsText('Hello World'));
  ///       });
  ///     });
  ///
  
negative.code: ///           const Provider(TextFormatter, useClass: AllCapsTextFormatter),
  ///         ]);
  ///         fixture = await bed.create();
  ///         expect(fixture.text, contains('HELLO WORLD'));
  ///       });
  ///     });
  class NgTestBed<T> {
  