anchor.diff:    });
   }
   
  -double? _getTranslationOffset(
  +double _getTranslationOffset(
     String key,
     WidgetTester tester,
     SharedAxisTransitionType transitionType,
  
positive.code:         return a + translation.y;
        });
      case SharedAxisTransitionType.scaled:
        // SharedAxisTransitionType.scaled should not return a translation
        // offset.
        return null;
    }
  }
  
  
negative.code:         // Bottom route is fully faded out.
          expect(find.text(bottomRoute), findsOneWidget);
          expect(_getOpacity(bottomRoute, tester), 0.0);
          final double halfwayBottomOffset = _getTranslationOffset(
            bottomRoute,
            tester,
            SharedAxisTransitionType.horizontal,
  