anchor.diff:      testWidgets('quick successive tap-selects vibrate once', (WidgetTester tester) async {
         Point center = await startPicker(tester, (TimeOfDay time) { });
         await tester.tapAt(new Point(center.x, center.y - 50.0));
  -      await tester.pump(kFastFeedbackInteral);
  +      await tester.pump(kFastFeedbackInterval);
         await tester.tapAt(new Point(center.x, center.y + 50.0));
         await finishPicker(tester);
         expect(hapticFeedbackCount, 1);
  
positive.code: 
        TestGesture gesture = await tester.startGesture(hour3);
        await gesture.moveBy(hour0 - hour3);
        await tester.pump(kSlowFeedbackInteral);
        await gesture.moveBy(hour3 - hour0);
        await tester.pump(kSlowFeedbackInteral);
        await gesture.moveBy(hour0 - hour3);
        await gesture.up();
        await finishPicker(tester);
  
negative.code:   });
  
    group('haptic feedback', () {
      const Duration kFastFeedbackInterval = const Duration(milliseconds: 10);
      const Duration kSlowFeedbackInterval = const Duration(milliseconds: 200);
      int hapticFeedbackCount;
  
      setUpAll(() {
  