anchor.diff:            );
     }
   }
  +
  +class DummyStatefulWidget extends StatefulWidget {
  +  const DummyStatefulWidget({Key? key}) : super(key: key);
  +
  +  @override
  +  State<StatefulWidget> createState() => DummyState();
  +}
  +
  +class DummyState extends State<DummyStatefulWidget> {
  +  @override
  +  Widget build(BuildContext context) => const SizedBox.expand();
  +}
  
positive.code:     await tester.tap(find.text('Closed'));
      await tester.pump(const Duration(milliseconds: 200));
  
      final State stateOpening = tester.state(find.byType(Switch));
      expect(stateOpening, isNotNull);
  
      await tester.pumpAndSettle();
      expect(find.text('Closed'), findsNothing);
      final State stateOpen = tester.state(find.byType(Switch));
      expect(stateOpen, isNotNull);
      expect(stateOpen, same(stateOpening));
  
  
negative.code:     navigator.pop();
      await tester.pump(const Duration(milliseconds: 200));
      expect(find.text('Open'), findsOneWidget);
      final State stateClosing = tester.state(find.byType(DummyStatefulWidget));
      expect(stateClosing, same(stateOpen));
  
      await tester.pumpAndSettle();
      expect(find.text('Open'), findsNothing);
      final State stateClosedAgain =
          tester.state(find.byType(DummyStatefulWidget));
      expect(stateClosedAgain, same(stateClosing));
    });
  
  