How to test mouse scroll event on flutter widget tests?

Question

I've wrapped up PageView widget inside a Listener widget. There I check in onPointerSignal property if pointerSignal is PointerScrollEvent to detect if the user used the mouse wheel to scroll on the widget. Then instead of doing the weird behaviour it produces I animateToPage and I set physics property of the PageView to NeverScrollableScrollPhysics() so it does not interfere with animateToPage transition.

That is working really cool! It jumps from one page to another with a smooth animation by moving mouse wheel.

But fun comes when testing the behaviour through widget testing. Does someone know how to emit/dispatch a PointerScrollEvent? I've tried the following without any success.

void main() {
  testWidgets(
    'when mouse wheel moved forward then next page is shown',
    (WidgetTester tester) async {
      await tester.pumpWidget(
        Test(
          child: PointerAwarePageView(
            children: [
              Text('1'),
              Text('2'),
            ],
          ),
        ),
      );

      expect(find.text('1'), findsOneWidget);

      tester.dispatchEvent(
        PointerScrollEvent(scrollDelta: Offset(0.0, 1.0)),
        HitTestResult(),
      );
      await tester.pump(Duration(seconds: 3));

      expect(find.text('2'), findsOneWidget);
    },
  );
}

Does it help you? github.com/flutter/flutter/blob/master/packages/flutter/test/… — Akif
– Akif, Commented Oct 17, 2020 at 19:59
@Akif unfortunately not, in that test they are not actually triggering the event. I need to know whcih specific function from WidgetTester allows me to fire a PointerScrollEvent — Lukard
– Lukard, Commented Oct 18, 2020 at 6:00

Lukard · Accepted Answer · 2020-10-20 17:45:47Z

Finally, I found a way to do it. This flutter test inspired me: https://github.com/flutter/flutter/blob/master/packages/flutter/test/widgets/scrollable_test.dart#L316

We need to create a TestPointer with mouse device kind and perform scroll. Then send the event though WidgetTester.

I will write down here my working resulting test:

void main() {
  testWidgets(
    'when mouse wheel is scrolled then next page is shown',
    (WidgetTester tester) async {
      await tester.pumpWidget(
        Test(
          child: PointerAwarePageView(
            children: [
              Text('1'),
              Text('2'),
            ],
          ),
        ),
      );

      expect(find.text('1'), findsOneWidget);

      final Offset scrollEventLocation = tester.getCenter(find.byType(PointerAwarePageView));
      final TestPointer testPointer = TestPointer(1, PointerDeviceKind.mouse);
      testPointer.hover(scrollEventLocation);
      final HitTestResult result = tester.hitTestOnBinding(scrollEventLocation);
      await tester.sendEventToBinding(testPointer.scroll(const Offset(0.0, 1.0)), result);
      await tester.pumpAndSettle();

      expect(find.text('2'), findsOneWidget);
    },
  );
}

Collectives™ on Stack Overflow

How to test mouse scroll event on flutter widget tests?

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related