verifySystemNavigatorPop function

Future<void> verifySystemNavigatorPop(WidgetTester tester)

To verify pressing back button, leaves the app

Sources:

1. https://github.com/flutter/packages/blob/cda21a89692739a3250091f061f9ac9d4bb8060e/packages/go_router/test/go_router_test.dart#L753-L795
2. https://github.com/flutter/flutter/blob/3b4ac4d5cc59344170833b93a968ace003f184f0/packages/flutter/test/services/system_navigator_test.dart#L12-L30

Implementation

Future<void> verifySystemNavigatorPop(WidgetTester tester) async {
  final List<MethodCall> log = <MethodCall>[];
  TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
      .setMockMethodCallHandler(SystemChannels.platform,
          (MethodCall methodCall) async {
    log.add(methodCall);
    return null;
  });

  Future<void> verify(AsyncCallback test, List<Object> expectations) async {
    log.clear();
    await test();
    expect(log, expectations);
  }

  await tester.runAsync(() async {
    await verify(() => simulateAndroidBackButton(tester), <Object>[
      isMethodCall('SystemNavigator.pop', arguments: null),
    ]);
  });

  TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
      .setMockMethodCallHandler(SystemChannels.platform, null);
}