anchor.diff:      final TestGesture gesture = await tester.startGesture(const Offset(5, 200));
       // Move right a bit
       await gesture.moveBy(const Offset(300, 0));
  -    verify(navigatorObserver.didStartUserGesture(any, any)).called(1);
  +    expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didStartUserGesture);
       expect(
         tester.state<NavigatorState>(find.byType(Navigator)).userGestureInProgress,
         true,
  
positive.code:     // Back to the page covering the whole screen.
      expect(tester.getTopLeft(find.text('2')).dx, moreOrLessEquals(0));
      expect(navigatorKey.currentState.userGestureInProgress, false);
      verify(navigatorObserver.didStopUserGesture()).called(1);
      verifyNever(navigatorObserver.didPop(any, any));
  
      await tester.dragFrom(const Offset(5, 100), const Offset(500, 0));
      await tester.pump();
      expect(tester.getTopLeft(find.text('2')).dx, moreOrLessEquals(500));
      expect(navigatorKey.currentState.userGestureInProgress, true);
      verify(navigatorObserver.didPop(any, any)).called(1);
  
      // Did go far enough to snap out of this route.
      await tester.pump(const Duration(milliseconds: 301));
  
negative.code:     final TestGesture gesture = await tester.startGesture(const Offset(5, 200));
      // The width of the page.
      await gesture.moveBy(const Offset(800, 0));
      expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didStartUserGesture);
      await gesture.up();
      await tester.pump();
  
      expect(find.text('Page 1'), isOnstage);
      expect(find.text('Page 2'), findsNothing);
      expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didStopUserGesture);
      expect(navigatorObserver.invocations.removeLast(), NavigatorInvocation.didPop);
    });
  
    testWidgets('test edge swipe then drop back at starting point works', (WidgetTester tester) async {
  