anchor.diff:      codecCompleter.complete(mockCodec);
       await tester.idle();
   
  -    final FrameInfo frame1 = FakeFrameInfo(20, 10, const Duration(milliseconds: 200));
  +    final FrameInfo frame1 = FakeFrameInfo(const Duration(milliseconds: 200), image20x10);
       mockCodec.completeNextFrame(frame1);
       await tester.idle();
       // We are waiting for the next animation tick, so at this point no frames
  
positive.code: import 'package:meta/meta.dart';
  
  class FakeFrameInfo implements FrameInfo {
    FakeFrameInfo(int width, int height, this._duration)
      : _image = FakeImage(width, height);
  
    final Duration _duration;
    final Image _image;
  
negative.code:     codecCompleter.complete(mockCodec);
      await tester.idle();
  
      final FrameInfo frame1 = FakeFrameInfo(const Duration(milliseconds: 200), image20x10);
      final FrameInfo frame2 = FakeFrameInfo(const Duration(milliseconds: 400), image200x100);
  
      mockCodec.completeNextFrame(frame1);
      await tester.idle(); // let nextFrameFuture complete
  