anchor.diff:  import 'dart:ui' as ui;
   
   import 'package:flutter/foundation.dart';
  -import 'package:flutter/services.dart';
  -import 'package:flutter_test/flutter_test.dart';
   import 'package:flutter/material.dart';
   import 'package:flutter/rendering.dart';
  +import 'package:flutter/scheduler.dart';
  +import 'package:flutter/services.dart';
  +
  +import 'package:flutter_test/flutter_test.dart';
   
   Future<void> pumpTest(
     WidgetTester tester,
  
positive.code:     return ExtraSuperPessimisticScrollPhysics(parent: buildParent(ancestor));
    }
  }
  
negative.code:     expect(targetMidRightPage1, findsOneWidget);
      expect(targetMidLeftPage1, findsOneWidget);
    });
  
    testWidgets('ensureVisible does not move TabViews', (WidgetTester tester) async {
      final TickerProvider vsync = TestTickerProvider();
      final TabController controller = TabController(
        length: 3,
        vsync: vsync,
      );
  
      await tester.pumpWidget(
        Directionality(
          textDirection: TextDirection.ltr,
          child: TabBarView(
            controller: controller,
            children: List<ListView>.generate(
              3,
              (int pageIndex) {
                return ListView(
                  key: Key('list_$pageIndex'),
                  children: List<Widget>.generate(
                    100,
                    (int listIndex) {
                      return Row(
                        children: <Widget>[
                          Container(
                            key: Key('${pageIndex}_${listIndex}_0'),
                            color: Colors.red,
                            width: 200,
                            height: 10,
                          ),
                          Container(
                            key: Key('${pageIndex}_${listIndex}_1'),
                            color: Colors.blue,
                            width: 200,
                            height: 10,
                          ),
                          Container(
                            key: Key('${pageIndex}_${listIndex}_2'),
                            color: Colors.green,
                            width: 200,
                            height: 10,
                          ),
                        ]
                      );
                    }
                  ),
                );
              }
            )
          ),
        ),
      );
  
      final Finder targetMidRightPage0 = find.byKey(const Key('0_25_2'));
      final Finder targetMidRightPage1 = find.byKey(const Key('1_25_2'));
      final Finder targetMidLeftPage1 = find.byKey(const Key('1_25_0'));
  
      expect(find.byKey(const Key('list_0')), findsOneWidget);
      expect(find.byKey(const Key('list_1')), findsNothing);
      expect(targetMidRightPage0, findsOneWidget);
      expect(targetMidRightPage1, findsNothing);
      expect(targetMidLeftPage1, findsNothing);
  
      await tester.ensureVisible(targetMidRightPage0);
      await tester.pumpAndSettle();
      expect(targetMidRightPage0, findsOneWidget);
      expect(targetMidRightPage1, findsNothing);
      expect(targetMidLeftPage1, findsNothing);
  
      controller.index = 1;
      await tester.pumpAndSettle();
  
      expect(find.byKey(const Key('list_0')), findsNothing);
      expect(find.byKey(const Key('list_1')), findsOneWidget);
      await tester.ensureVisible(targetMidRightPage1);
      await tester.pumpAndSettle();
  
      expect(targetMidRightPage0, findsNothing);
      expect(targetMidRightPage1, findsOneWidget);
      expect(targetMidLeftPage1, findsOneWidget);
  
      await tester.ensureVisible(targetMidLeftPage1);
      await tester.pumpAndSettle();
  
      expect(targetMidRightPage0, findsNothing);
      expect(targetMidRightPage1, findsOneWidget);
      expect(targetMidLeftPage1, findsOneWidget);
    });
  }
  
  // ignore: must_be_immutable
  