I want to test my AnimatedPositioned widget’s proper animation, so here is my code and it’s widget test:

Code:

AnimatedPositioned(
  key: const Key('get_started_overlay'),
  duration: const Duration(milliseconds: 500),
  curve: Curves.easeInOut,
  left: 0,
  right: 0,
  top: isOverlayVisible ? 0 : size.height,
  child: Child()
),

Test:

testWidgets(
  'proper functioning of AnimatedPositioned animation',
  (widgetTester) async {
    await widgetTester.pumpWidget(
      const MediaQuery(
        data: MediaQueryData(size: Size(2560, 1600)),
        child: GetStartedScreen(),
      ),
    );

    expect(
      widgetTester
          .widget<AnimatedPositioned>(
              find.byKey(const Key('get_started_overlay')))
          .top,
      1600,
    );

    await widgetTester.tap(find.byKey(Key('intro_video_widget')));
    await widgetTester.pump(const Duration(milliseconds: 250));

    expect(
      widgetTester
          .widget<AnimatedPositioned>(
              find.byKey(const Key('get_started_overlay')))
          .top,
      800,
    );
  },
);

Here, after 250 ms, I was actually expecting the animation to be more or less the half way there (top: 800)… But, I got the error saying:

The following TestFailure was thrown running a test:
Expected: <800>
  Actual: <0.0>

So, I want to be able to put breakpoint, so I could figured out what is wrong with the code and why it throws the aforementioned error, any help would be appreciated !