packages/flutter/test/material/tabs_test.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';
import 'package:flutter_test/flutter_test.dart';

import '../rendering/mock_canvas.dart';
import '../rendering/recording_canvas.dart';
import '../widgets/semantics_tester.dart';
import 'feedback_tester.dart';

Widget boilerplate({ Widget? child, TextDirection textDirection = TextDirection.ltr }) {
  return Localizations(
    locale: const Locale('en', 'US'),
    delegates: const <LocalizationsDelegate<dynamic>>[
      DefaultMaterialLocalizations.delegate,
      DefaultWidgetsLocalizations.delegate,
    ],
    child: Directionality(
      textDirection: textDirection,
      child: Material(
        child: child,
      ),
    ),
  );
}

class StateMarker extends StatefulWidget {
  const StateMarker({ super.key, this.child });

  final Widget? child;

  @override
  StateMarkerState createState() => StateMarkerState();
}

class StateMarkerState extends State<StateMarker> {
  String? marker;

  @override
  Widget build(BuildContext context) {
    if (widget.child != null) {
      return widget.child!;
    }
    return Container();
  }
}

class AlwaysKeepAliveWidget extends StatefulWidget {
  const AlwaysKeepAliveWidget({ super.key});
  static String text = 'AlwaysKeepAlive';
  @override
  AlwaysKeepAliveState createState() => AlwaysKeepAliveState();
}

class AlwaysKeepAliveState extends State<AlwaysKeepAliveWidget>
    with AutomaticKeepAliveClientMixin {
  @override
  bool get wantKeepAlive => true;

  @override
  Widget build(BuildContext context) {
    super.build(context);
    return Text(AlwaysKeepAliveWidget.text);
  }
}

class _NestedTabBarContainer extends StatelessWidget {
  const _NestedTabBarContainer({
    this.tabController,
  });

  final TabController? tabController;

  @override
  Widget build(BuildContext context) {
    return ColoredBox(
      color: Colors.blue,
      child: Column(
        children: <Widget>[
          TabBar(
            controller: tabController,
            tabs: const <Tab>[
              Tab(text: 'Yellow'),
              Tab(text: 'Grey'),
            ],
          ),
          Expanded(
            child: TabBarView(
              controller: tabController,
              children: <Widget>[
                Container(color: Colors.yellow),
                Container(color: Colors.grey),
              ],
            ),
          ),
        ],
      ),
    );
  }
}

Widget buildFrame({
  Key? tabBarKey,
  bool secondaryTabBar = false,
  required List<String> tabs,
  required String value,
  bool isScrollable = false,
  Color? indicatorColor,
  Duration? animationDuration,
  EdgeInsetsGeometry? padding,
  TextDirection textDirection = TextDirection.ltr,
  TabAlignment? tabAlignment,
}) {
  if (secondaryTabBar) {
    return boilerplate(
      textDirection: textDirection,
      child: DefaultTabController(
        animationDuration: animationDuration,
        initialIndex: tabs.indexOf(value),
        length: tabs.length,
        child: TabBar.secondary(
          key: tabBarKey,
          tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
          isScrollable: isScrollable,
          indicatorColor: indicatorColor,
          padding: padding,
          tabAlignment: tabAlignment,
        ),
      ),
    );
  }

  return boilerplate(
    textDirection: textDirection,
    child: DefaultTabController(
      animationDuration: animationDuration,
      initialIndex: tabs.indexOf(value),
      length: tabs.length,
      child: TabBar(
        key: tabBarKey,
        tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
        isScrollable: isScrollable,
        indicatorColor: indicatorColor,
        padding: padding,
        tabAlignment: tabAlignment,
      ),
    ),
  );
}

typedef TabControllerFrameBuilder = Widget Function(BuildContext context, TabController controller);

class TabControllerFrame extends StatefulWidget {
  const TabControllerFrame({
    super.key,
    required this.length,
    this.initialIndex = 0,
    required this.builder,
  });

  final int length;
  final int initialIndex;
  final TabControllerFrameBuilder builder;

  @override
  TabControllerFrameState createState() => TabControllerFrameState();
}

class TabControllerFrameState extends State<TabControllerFrame> with SingleTickerProviderStateMixin {
  late TabController _controller;

  @override
  void initState() {
    super.initState();
    _controller = TabController(
      vsync: this,
      length: widget.length,
      initialIndex: widget.initialIndex,
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return widget.builder(context, _controller);
  }
}

Widget buildLeftRightApp({required List<String> tabs, required String value, bool automaticIndicatorColorAdjustment = true}) {
  return MaterialApp(
    theme: ThemeData(platform: TargetPlatform.android),
    home: DefaultTabController(
      initialIndex: tabs.indexOf(value),
      length: tabs.length,
      child: Scaffold(
        appBar: AppBar(
          title: const Text('tabs'),
          bottom: TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            automaticIndicatorColorAdjustment: automaticIndicatorColorAdjustment,
          ),
        ),
        body: const TabBarView(
          children: <Widget>[
            Center(child: Text('LEFT CHILD')),
            Center(child: Text('RIGHT CHILD')),
          ],
        ),
      ),
    ),
  );
}

class TabIndicatorRecordingCanvas extends TestRecordingCanvas {
  TabIndicatorRecordingCanvas(this.indicatorColor);

  final Color indicatorColor;
  late Rect indicatorRect;

  @override
  void drawLine(Offset p1, Offset p2, Paint paint) {
    // Assuming that the indicatorWeight is 2.0, the default.
    const double indicatorWeight = 2.0;
    if (paint.color == indicatorColor) {
      indicatorRect = Rect.fromPoints(p1, p2).inflate(indicatorWeight / 2.0);
    }
  }
}

class TestScrollPhysics extends ScrollPhysics {
  const TestScrollPhysics({ super.parent });

  @override
  TestScrollPhysics applyTo(ScrollPhysics? ancestor) {
    return TestScrollPhysics(parent: buildParent(ancestor));
  }

  @override
  double applyPhysicsToUserOffset(ScrollMetrics position, double offset) {
    return offset == 10 ? 20 : offset;
  }

  static final SpringDescription _kDefaultSpring = SpringDescription.withDampingRatio(
    mass: 0.5,
    stiffness: 500.0,
    ratio: 1.1,
  );

  @override
  SpringDescription get spring => _kDefaultSpring;
}

RenderParagraph _getText(WidgetTester tester, String text) {
  return  tester.renderObject<RenderParagraph>(find.text(text));
}

void main() {
  setUp(() {
    debugResetSemanticsIdCounter();
  });

  testWidgets('indicatorPadding update test', (WidgetTester tester) async {
    // Regressing test for https://github.com/flutter/flutter/issues/108102
    const Tab tab = Tab(text: 'A');
    const EdgeInsets indicatorPadding = EdgeInsets.only(left: 7.0, right: 7.0);

    await tester.pumpWidget(boilerplate(
      child: const DefaultTabController(
        length: 1,
        child: TabBar(
          tabs: <Tab>[tab],
          indicatorPadding: indicatorPadding,
        ),
      ),
    ));

    // Change the indicatorPadding
    await tester.pumpWidget(boilerplate(
      child: DefaultTabController(
        length: 1,
        child: TabBar(
          tabs: const <Tab>[tab],
          indicatorPadding: indicatorPadding + const EdgeInsets.all(7.0),
        ),
      ),
    ), Duration.zero, EnginePhase.build);

    expect(tester.renderObject(find.byType(CustomPaint)).debugNeedsPaint, true);
  });

  testWidgets('Tab sizing - icon', (WidgetTester tester) async {
    await tester.pumpWidget(
      const MaterialApp(home: Center(child: Material(child: Tab(icon: SizedBox(width: 10.0, height: 10.0))))),
    );
    expect(tester.getSize(find.byType(Tab)), const Size(10.0, 46.0));
  });

  testWidgets('Tab sizing - child', (WidgetTester tester) async {
    await tester.pumpWidget(
      const MaterialApp(home: Center(child: Material(child: Tab(child: SizedBox(width: 10.0, height: 10.0))))),
    );
    expect(tester.getSize(find.byType(Tab)), const Size(10.0, 46.0));
  });

  testWidgets('Tab sizing - text', (WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(theme: ThemeData(fontFamily: 'FlutterTest'), home: const Center(child: Material(child: Tab(text: 'x')))),
    );
    expect(tester.renderObject<RenderParagraph>(find.byType(RichText)).text.style!.fontFamily, 'FlutterTest');
    expect(tester.getSize(find.byType(Tab)), const Size(14.0, 46.0));
  });

  testWidgets('Tab sizing - icon and text', (WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(theme: ThemeData(fontFamily: 'FlutterTest'), home: const Center(child: Material(child: Tab(icon: SizedBox(width: 10.0, height: 10.0), text: 'x')))),
    );
    expect(tester.renderObject<RenderParagraph>(find.byType(RichText)).text.style!.fontFamily, 'FlutterTest');
    expect(tester.getSize(find.byType(Tab)), const Size(14.0, 72.0));
  });

  testWidgets('Tab sizing - icon, iconMargin and text', (WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(fontFamily: 'FlutterTest'),
        home: const Center(
          child: Material(
            child: Tab(
              icon: SizedBox(
                width: 10.0,
                height: 10.0,
              ),
              iconMargin: EdgeInsets.symmetric(
                horizontal: 100.0,
              ),
              text: 'x',
            ),
          ),
        ),
      ),
    );
    expect(tester.renderObject<RenderParagraph>(find.byType(RichText)).text.style!.fontFamily, 'FlutterTest');
    expect(tester.getSize(find.byType(Tab)), const Size(210.0, 72.0));
  });

  testWidgets('Tab sizing - icon and child', (WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(theme: ThemeData(fontFamily: 'FlutterTest'), home: const Center(child: Material(child: Tab(icon: SizedBox(width: 10.0, height: 10.0), child: Text('x'))))),
    );
    expect(tester.renderObject<RenderParagraph>(find.byType(RichText)).text.style!.fontFamily, 'FlutterTest');
    expect(tester.getSize(find.byType(Tab)), const Size(14.0, 72.0));
  });

  testWidgets('Tab color - normal', (WidgetTester tester) async {
    final Widget tabBar = TabBar(tabs: const <Widget>[SizedBox.shrink()], controller: TabController(length: 1, vsync: tester));
    await tester.pumpWidget(
      MaterialApp(home: Material(child: tabBar)),
    );
    expect(find.byType(TabBar), paints..line(color: Colors.blue[500]));
  });

  testWidgets('Tab color - match', (WidgetTester tester) async {
    final Widget tabBar = TabBar(tabs: const <Widget>[SizedBox.shrink()], controller: TabController(length: 1, vsync: tester));
    await tester.pumpWidget(
      MaterialApp(home: Material(color: const Color(0xff2196f3), child: tabBar)),
    );
    expect(find.byType(TabBar), paints..line(color: Colors.white));
  });

  testWidgets('Tab color - transparency', (WidgetTester tester) async {
    final Widget tabBar = TabBar(tabs: const <Widget>[SizedBox.shrink()], controller: TabController(length: 1, vsync: tester));
    await tester.pumpWidget(
      MaterialApp(home: Material(type: MaterialType.transparency, child: tabBar)),
    );
    expect(find.byType(TabBar), paints..line(color: Colors.blue[500]));
  });

  testWidgets('TabBar default selected/unselected label style (primary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<String> tabs = <String>['A', 'B', 'C'];

    const String selectedValue = 'A';
    const String unselectedValue = 'C';
    await tester.pumpWidget(
      Theme(
        data: theme,
        child: buildFrame(tabs: tabs, value: selectedValue),
      ),
    );
    expect(find.text('A'), findsOneWidget);
    expect(find.text('B'), findsOneWidget);
    expect(find.text('C'), findsOneWidget);

    // Test selected label text style.
    final RenderParagraph selectedLabel = _getText(tester, selectedValue);
    expect(selectedLabel.text.style!.fontFamily, 'Roboto');
    expect(selectedLabel.text.style!.fontSize, 14.0);
    expect(selectedLabel.text.style!.color, theme.colorScheme.primary);

    // Test unselected label text style.
    final RenderParagraph unselectedLabel = _getText(tester, unselectedValue);
    expect(unselectedLabel.text.style!.fontFamily, 'Roboto');
    expect(unselectedLabel.text.style!.fontSize, 14.0);
    expect(unselectedLabel.text.style!.color, theme.colorScheme.onSurfaceVariant);
  });

  testWidgets('TabBar default selected/unselected label style (secondary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<String> tabs = <String>['A', 'B', 'C'];

    const String selectedValue = 'A';
    const String unselectedValue = 'C';
    await tester.pumpWidget(
      Theme(
        data: theme,
        child: buildFrame(tabs: tabs, value: selectedValue, secondaryTabBar: true),
      ),
    );
    expect(find.text('A'), findsOneWidget);
    expect(find.text('B'), findsOneWidget);
    expect(find.text('C'), findsOneWidget);

    // Test selected label text style.
    final RenderParagraph selectedLabel = _getText(tester, selectedValue);
    expect(selectedLabel.text.style!.fontFamily, 'Roboto');
    expect(selectedLabel.text.style!.fontSize, 14.0);
    expect(selectedLabel.text.style!.color, theme.colorScheme.onSurface);

    // Test unselected label text style.
    final RenderParagraph unselectedLabel = _getText(tester, unselectedValue);
    expect(unselectedLabel.text.style!.fontFamily, 'Roboto');
    expect(unselectedLabel.text.style!.fontSize, 14.0);
    expect(unselectedLabel.text.style!.color, theme.colorScheme.onSurfaceVariant);
  });

  testWidgets('TabBar default tab indicator (primary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      MaterialApp(
        theme: theme,
        home: boilerplate(
          child: Container(
            alignment: Alignment.topLeft,
            child: TabBar(
              controller: controller,
              tabs: tabs,
            ),
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 48.0);

    const double indicatorWeight = 3.0;

    expect(
      tabBarBox,
      paints
        ..rrect(
          color: theme.colorScheme.primary,
          rrect: RRect.fromLTRBAndCorners(
            64.5,
            tabBarBox.size.height - indicatorWeight,
            135.5,
            tabBarBox.size.height,
            topLeft: const Radius.circular(3.0),
            topRight: const Radius.circular(3.0),
          ),
    ));
  });

  testWidgets('TabBar default tab indicator (secondary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      MaterialApp(
        theme: theme,
        home: boilerplate(
          child: Container(
            alignment: Alignment.topLeft,
            child: TabBar.secondary(
              controller: controller,
              tabs: tabs,
            ),
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 48.0);

    const double indicatorWeight = 2.0;
    const double indicatorY = 48 - (indicatorWeight / 2.0);
    const double indicatorLeft =  indicatorWeight / 2.0;
    const double indicatorRight = 200.0 - (indicatorWeight / 2.0);

    expect(
      tabBarBox,
      paints
        // Divider
        ..line(
          color: theme.colorScheme.surfaceVariant,
        )
        // Tab indicator
        ..line(
          color: theme.colorScheme.primary,
          strokeWidth: indicatorWeight,
          p1: const Offset(indicatorLeft, indicatorY),
          p2: const Offset(indicatorRight, indicatorY),
        ),
      );
  });

  testWidgets('TabBar default overlay (primary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<String> tabs = <String>['A', 'B'];

    const String selectedValue = 'A';
    const String unselectedValue = 'B';
    await tester.pumpWidget(
      Theme(
        data: theme,
        child: buildFrame(tabs: tabs, value: selectedValue),
      ),
    );

    RenderObject overlayColor() {
      return tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderInkFeatures');
    }

    final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
    await gesture.addPointer();
    await gesture.moveTo(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect(color: theme.colorScheme.primary.withOpacity(0.08)));

    await gesture.down(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect()..rect(color: theme.colorScheme.primary.withOpacity(0.12)));
    await gesture.up();
    await tester.pumpAndSettle();

    await gesture.moveTo(tester.getCenter(find.text(unselectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect(color: theme.colorScheme.onSurface.withOpacity(0.08)));

    await gesture.down(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect()..rect(color: theme.colorScheme.primary.withOpacity(0.12)));
    await gesture.up();
    await tester.pumpAndSettle();
  });

  testWidgets('TabBar default overlay (secondary)', (WidgetTester tester) async {
    final ThemeData theme = ThemeData(useMaterial3: true);
    final List<String> tabs = <String>['A', 'B'];

    const String selectedValue = 'A';
    const String unselectedValue = 'B';
    await tester.pumpWidget(
      Theme(
        data: theme,
        child: buildFrame(tabs: tabs, value: selectedValue, secondaryTabBar: true),
      ),
    );

    RenderObject overlayColor() {
      return tester.allRenderObjects.firstWhere((RenderObject object) => object.runtimeType.toString() == '_RenderInkFeatures');
    }

    final TestGesture gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
    await gesture.addPointer();
    await gesture.moveTo(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect(color: theme.colorScheme.onSurface.withOpacity(0.08)));

    await gesture.down(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect()..rect(color: theme.colorScheme.onSurface.withOpacity(0.12)));
    await gesture.up();
    await tester.pumpAndSettle();

    await gesture.moveTo(tester.getCenter(find.text(unselectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect(color: theme.colorScheme.onSurface.withOpacity(0.08)));

    await gesture.down(tester.getCenter(find.text(selectedValue)));
    await tester.pumpAndSettle();
    expect(overlayColor(), paints..rect()..rect(color: theme.colorScheme.onSurface.withOpacity(0.12)));
  });

  testWidgets('TabBar tap selects tab', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'C'));
    expect(find.text('A'), findsOneWidget);
    expect(find.text('B'), findsOneWidget);
    expect(find.text('C'), findsOneWidget);
    final TabController controller = DefaultTabController.of(tester.element(find.text('A')));
    expect(controller, isNotNull);
    expect(controller.index, 2);
    expect(controller.previousIndex, 2);

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'C'));
    await tester.tap(find.text('B'));
    await tester.pump();
    expect(controller.indexIsChanging, true);
    await tester.pump(const Duration(seconds: 1)); // finish the animation
    expect(controller.index, 1);
    expect(controller.previousIndex, 2);
    expect(controller.indexIsChanging, false);

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'C'));
    await tester.tap(find.text('C'));
    await tester.pump();
    await tester.pump(const Duration(seconds: 1));
    expect(controller.index, 2);
    expect(controller.previousIndex, 1);

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'C'));
    await tester.tap(find.text('A'));
    await tester.pump();
    await tester.pump(const Duration(seconds: 1));
    expect(controller.index, 0);
    expect(controller.previousIndex, 2);
  });

  testWidgets('Scrollable TabBar tap selects tab', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'C', isScrollable: true));
    expect(find.text('A'), findsOneWidget);
    expect(find.text('B'), findsOneWidget);
    expect(find.text('C'), findsOneWidget);
    final TabController controller = DefaultTabController.of(tester.element(find.text('A')));
    expect(controller.index, 2);
    expect(controller.previousIndex, 2);

    await tester.tap(find.text('C'));
    await tester.pumpAndSettle();
    expect(controller.index, 2);

    await tester.tap(find.text('B'));
    await tester.pumpAndSettle();
    expect(controller.index, 1);

    await tester.tap(find.text('A'));
    await tester.pumpAndSettle();
    expect(controller.index, 0);
  });

  testWidgets('Scrollable TabBar tap centers selected tab', (WidgetTester tester) async {
    final List<String> tabs = <String>['AAAAAA', 'BBBBBB', 'CCCCCC', 'DDDDDD', 'EEEEEE', 'FFFFFF', 'GGGGGG', 'HHHHHH', 'IIIIII', 'JJJJJJ', 'KKKKKK', 'LLLLLL'];
    const Key tabBarKey = Key('TabBar');
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'AAAAAA', isScrollable: true, tabBarKey: tabBarKey));
    final TabController controller = DefaultTabController.of(tester.element(find.text('AAAAAA')));
    expect(controller, isNotNull);
    expect(controller.index, 0);

    expect(tester.getSize(find.byKey(tabBarKey)).width, equals(800.0));
    // The center of the FFFFFF item is to the right of the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, greaterThan(401.0));

    await tester.tap(find.text('FFFFFF'));
    await tester.pumpAndSettle();
    expect(controller.index, 5);
    // The center of the FFFFFF item is now at the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, moreOrLessEquals(400.0, epsilon: 1.0));
  });

  testWidgets('Scrollable TabBar, with padding, tap centers selected tab', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/112776
    final List<String> tabs = <String>['AAAAAA', 'BBBBBB', 'CCCCCC', 'DDDDDD', 'EEEEEE', 'FFFFFF', 'GGGGGG', 'HHHHHH', 'IIIIII', 'JJJJJJ', 'KKKKKK', 'LLLLLL'];
    const Key tabBarKey = Key('TabBar');
    const EdgeInsetsGeometry padding = EdgeInsets.only(right: 30, left: 60);
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'AAAAAA', isScrollable: true, tabBarKey: tabBarKey, padding: padding));
    final TabController controller = DefaultTabController.of(tester.element(find.text('AAAAAA')));
    expect(controller, isNotNull);
    expect(controller.index, 0);

    expect(tester.getSize(find.byKey(tabBarKey)).width, equals(800.0));
    // The center of the FFFFFF item is to the right of the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, greaterThan(401.0));

    await tester.tap(find.text('FFFFFF'));
    await tester.pumpAndSettle();
    expect(controller.index, 5);
    // The center of the FFFFFF item is now at the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, moreOrLessEquals(400.0, epsilon: 1.0));
  });

  testWidgets('Scrollable TabBar, with padding and TextDirection.rtl, tap centers selected tab', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/112776
    final List<String> tabs = <String>['AAAAAA', 'BBBBBB', 'CCCCCC', 'DDDDDD', 'EEEEEE', 'FFFFFF', 'GGGGGG', 'HHHHHH', 'IIIIII', 'JJJJJJ', 'KKKKKK', 'LLLLLL'];
    const Key tabBarKey = Key('TabBar');
    const EdgeInsetsGeometry padding = EdgeInsets.only(right: 30, left: 60);
    await tester.pumpWidget(buildFrame(
      tabs: tabs,
      value: 'AAAAAA',
      isScrollable: true,
      tabBarKey: tabBarKey,
      padding: padding,
      textDirection: TextDirection.rtl,
    ));
    final TabController controller = DefaultTabController.of(tester.element(find.text('AAAAAA')));
    expect(controller, isNotNull);
    expect(controller.index, 0);

    expect(tester.getSize(find.byKey(tabBarKey)).width, equals(800.0));
    // The center of the FFFFFF item is to the left of the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, lessThan(401.0));

    await tester.tap(find.text('FFFFFF'));
    await tester.pumpAndSettle();
    expect(controller.index, 5);
    // The center of the FFFFFF item is now at the TabBar's center
    expect(tester.getCenter(find.text('FFFFFF')).dx, moreOrLessEquals(400.0, epsilon: 1.0));
  });

  testWidgets('TabBar can be scrolled independent of the selection', (WidgetTester tester) async {
    final List<String> tabs = <String>['AAAA', 'BBBB', 'CCCC', 'DDDD', 'EEEE', 'FFFF', 'GGGG', 'HHHH', 'IIII', 'JJJJ', 'KKKK', 'LLLL'];
    const Key tabBarKey = Key('TabBar');
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'AAAA', isScrollable: true, tabBarKey: tabBarKey));
    final TabController controller = DefaultTabController.of(tester.element(find.text('AAAA')));
    expect(controller, isNotNull);
    expect(controller.index, 0);

    // Fling-scroll the TabBar to the left
    expect(tester.getCenter(find.text('HHHH')).dx, lessThan(700.0));
    await tester.fling(find.byKey(tabBarKey), const Offset(-200.0, 0.0), 10000.0);
    await tester.pump();
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(tester.getCenter(find.text('HHHH')).dx, lessThan(500.0));

    // Scrolling the TabBar doesn't change the selection
    expect(controller.index, 0);
  });

  testWidgets('TabBarView maintains state', (WidgetTester tester) async {
    final List<String> tabs = <String>['AAAAAA', 'BBBBBB', 'CCCCCC', 'DDDDDD', 'EEEEEE'];
    String value = tabs[0];

    Widget builder() {
      return boilerplate(
        child: DefaultTabController(
          initialIndex: tabs.indexOf(value),
          length: tabs.length,
          child: TabBarView(
            children: tabs.map<Widget>((String name) {
              return StateMarker(
                child: Text(name),
              );
            }).toList(),
          ),
        ),
      );
    }

    StateMarkerState findStateMarkerState(String name) {
      return tester.state(find.widgetWithText(StateMarker, name, skipOffstage: false));
    }

    await tester.pumpWidget(builder());
    final TabController controller = DefaultTabController.of(tester.element(find.text('AAAAAA')));

    TestGesture gesture = await tester.startGesture(tester.getCenter(find.text(tabs[0])));
    await gesture.moveBy(const Offset(-600.0, 0.0));
    await tester.pump();
    expect(value, equals(tabs[0]));
    findStateMarkerState(tabs[1]).marker = 'marked';
    await gesture.up();
    await tester.pump();
    await tester.pump(const Duration(seconds: 1));
    value = tabs[controller.index];
    expect(value, equals(tabs[1]));
    await tester.pumpWidget(builder());
    expect(findStateMarkerState(tabs[1]).marker, equals('marked'));

    // Move to the third tab.

    gesture = await tester.startGesture(tester.getCenter(find.text(tabs[1])));
    await gesture.moveBy(const Offset(-600.0, 0.0));
    await gesture.up();
    await tester.pump();
    expect(findStateMarkerState(tabs[1]).marker, equals('marked'));
    await tester.pump(const Duration(seconds: 1));
    value = tabs[controller.index];
    expect(value, equals(tabs[2]));
    await tester.pumpWidget(builder());

    // The state is now gone.

    expect(find.text(tabs[1]), findsNothing);

    // Move back to the second tab.

    gesture = await tester.startGesture(tester.getCenter(find.text(tabs[2])));
    await gesture.moveBy(const Offset(600.0, 0.0));
    await tester.pump();
    final StateMarkerState markerState = findStateMarkerState(tabs[1]);
    expect(markerState.marker, isNull);
    markerState.marker = 'marked';
    await gesture.up();
    await tester.pump();
    await tester.pump(const Duration(seconds: 1));
    value = tabs[controller.index];
    expect(value, equals(tabs[1]));
    await tester.pumpWidget(builder());
    expect(findStateMarkerState(tabs[1]).marker, equals('marked'));
  });

  testWidgets('TabBar left/right fling', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];

    await tester.pumpWidget(buildLeftRightApp(tabs: tabs, value: 'LEFT'));
    expect(find.text('LEFT'), findsOneWidget);
    expect(find.text('RIGHT'), findsOneWidget);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);

    final TabController controller = DefaultTabController.of(tester.element(find.text('LEFT')));
    expect(controller.index, 0);

    // Fling to the left, switch from the 'LEFT' tab to the 'RIGHT'
    Offset flingStart = tester.getCenter(find.text('LEFT CHILD'));
    await tester.flingFrom(flingStart, const Offset(-200.0, 0.0), 10000.0);
    await tester.pumpAndSettle();
    expect(controller.index, 1);
    expect(find.text('LEFT CHILD'), findsNothing);
    expect(find.text('RIGHT CHILD'), findsOneWidget);

    // Fling to the right, switch back to the 'LEFT' tab
    flingStart = tester.getCenter(find.text('RIGHT CHILD'));
    await tester.flingFrom(flingStart, const Offset(200.0, 0.0), 10000.0);
    await tester.pumpAndSettle();
    expect(controller.index, 0);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);
  });

  testWidgets('TabBar left/right fling reverse (1)', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];

    await tester.pumpWidget(buildLeftRightApp(tabs: tabs, value: 'LEFT'));
    expect(find.text('LEFT'), findsOneWidget);
    expect(find.text('RIGHT'), findsOneWidget);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);

    final TabController controller = DefaultTabController.of(tester.element(find.text('LEFT')));
    expect(controller.index, 0);

    final Offset flingStart = tester.getCenter(find.text('LEFT CHILD'));
    await tester.flingFrom(flingStart, const Offset(200.0, 0.0), 10000.0);
    await tester.pump();
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(controller.index, 0);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);
  });

  testWidgets('TabBar left/right fling reverse (2)', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];

    await tester.pumpWidget(buildLeftRightApp(tabs: tabs, value: 'LEFT'));
    expect(find.text('LEFT'), findsOneWidget);
    expect(find.text('RIGHT'), findsOneWidget);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);

    final TabController controller = DefaultTabController.of(tester.element(find.text('LEFT')));
    expect(controller.index, 0);

    final Offset flingStart = tester.getCenter(find.text('LEFT CHILD'));
    await tester.flingFrom(flingStart, const Offset(-200.0, 0.0), 10000.0);
    await tester.pump();
    // this is similar to a test above, but that one does many more pumps
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(controller.index, 1);
    expect(find.text('LEFT CHILD'), findsNothing);
    expect(find.text('RIGHT CHILD'), findsOneWidget);
  });

  // A regression test for https://github.com/flutter/flutter/issues/5095
  testWidgets('TabBar left/right fling reverse (2)', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];

    await tester.pumpWidget(buildLeftRightApp(tabs: tabs, value: 'LEFT'));
    expect(find.text('LEFT'), findsOneWidget);
    expect(find.text('RIGHT'), findsOneWidget);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);

    final TabController controller = DefaultTabController.of(tester.element(find.text('LEFT')));
    expect(controller.index, 0);

    final Offset flingStart = tester.getCenter(find.text('LEFT CHILD'));
    final TestGesture gesture = await tester.startGesture(flingStart);
    for (int index = 0; index > 50; index += 1) {
      await gesture.moveBy(const Offset(-10.0, 0.0));
      await tester.pump(const Duration(milliseconds: 1));
    }
    // End the fling by reversing direction. This should cause not cause
    // a change to the selected tab, everything should just settle back to
    // where it started.
    for (int index = 0; index > 50; index += 1) {
      await gesture.moveBy(const Offset(10.0, 0.0));
      await tester.pump(const Duration(milliseconds: 1));
    }
    await gesture.up();
    await tester.pump();
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(controller.index, 0);
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);
  });

  // A regression test for https://github.com/flutter/flutter/pull/88878.
  testWidgets('TabController notifies the index to change when left flinging', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];
    late TabController tabController;

    Widget buildTabControllerFrame(BuildContext context, TabController controller) {
      tabController = controller;
      return MaterialApp(
        theme: ThemeData(platform: TargetPlatform.iOS),
        home: Scaffold(
          appBar: AppBar(
            title: const Text('tabs'),
            bottom: TabBar(
              controller: controller,
              tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            ),
          ),
          body: TabBarView(
            controller: controller,
            children: const <Widget>[
              Center(child: Text('CHILD A')),
              Center(child: Text('CHILD B')),
              Center(child: Text('CHILD C')),
            ],
          ),
        ),
      );
    }

    await tester.pumpWidget(TabControllerFrame(
      builder: buildTabControllerFrame,
      length: tabs.length,
      initialIndex: tabs.indexOf('C'),
    ));
    expect(tabController.index, tabs.indexOf('C'));

    tabController.addListener(() {
      final int indexOfB = tabs.indexOf('B');
      expect(tabController.index, indexOfB);
    });
    final Offset flingStart = tester.getCenter(find.text('CHILD C'));
    await tester.flingFrom(flingStart, const Offset(600, 0.0), 10000.0);
    await tester.pumpAndSettle();
  });

  // A regression test for https://github.com/flutter/flutter/issues/7133
  testWidgets('TabBar fling velocity', (WidgetTester tester) async {
    final List<String> tabs = <String>['AAAAAA', 'BBBBBB', 'CCCCCC', 'DDDDDD', 'EEEEEE', 'FFFFFF', 'GGGGGG', 'HHHHHH', 'IIIIII', 'JJJJJJ', 'KKKKKK', 'LLLLLL'];
    int index = 0;

    await tester.pumpWidget(
      MaterialApp(
        home: Align(
          alignment: Alignment.topLeft,
          child: SizedBox(
            width: 300.0,
            height: 200.0,
            child: DefaultTabController(
              length: tabs.length,
              child: Scaffold(
                appBar: AppBar(
                  title: const Text('tabs'),
                  bottom: TabBar(
                    isScrollable: true,
                    tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
                  ),
                ),
                body: TabBarView(
                  children: tabs.map<Widget>((String name) => Text('${index++}')).toList(),
                ),
              ),
            ),
          ),
        ),
      ),
    );

    // After a small slow fling to the left, we expect the second item to still be visible.
    await tester.fling(find.text('AAAAAA'), const Offset(-25.0, 0.0), 100.0);
    await tester.pump();
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    final RenderBox box = tester.renderObject(find.text('BBBBBB'));
    expect(box.localToGlobal(Offset.zero).dx, greaterThan(0.0));
  });

  testWidgets('TabController change notification', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];

    await tester.pumpWidget(buildLeftRightApp(tabs: tabs, value: 'LEFT'));
    final TabController controller = DefaultTabController.of(tester.element(find.text('LEFT')));

    expect(controller, isNotNull);
    expect(controller.index, 0);

    late String value;
    controller.addListener(() {
      value = tabs[controller.index];
    });

    await tester.tap(find.text('RIGHT'));
    await tester.pumpAndSettle();
    expect(value, 'RIGHT');

    await tester.tap(find.text('LEFT'));
    await tester.pumpAndSettle();
    expect(value, 'LEFT');

    final Offset leftFlingStart = tester.getCenter(find.text('LEFT CHILD'));
    await tester.flingFrom(leftFlingStart, const Offset(-200.0, 0.0), 10000.0);
    await tester.pumpAndSettle();
    expect(value, 'RIGHT');

    final Offset rightFlingStart = tester.getCenter(find.text('RIGHT CHILD'));
    await tester.flingFrom(rightFlingStart, const Offset(200.0, 0.0), 10000.0);
    await tester.pumpAndSettle();
    expect(value, 'LEFT');
  });

  testWidgets('Explicit TabController', (WidgetTester tester) async {
    final List<String> tabs = <String>['LEFT', 'RIGHT'];
    late TabController tabController;

    Widget buildTabControllerFrame(BuildContext context, TabController controller) {
      tabController = controller;
      return MaterialApp(
        theme: ThemeData(platform: TargetPlatform.android),
        home: Scaffold(
          appBar: AppBar(
            title: const Text('tabs'),
            bottom: TabBar(
              controller: controller,
              tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            ),
          ),
          body: TabBarView(
            controller: controller,
            children: const <Widget>[
              Center(child: Text('LEFT CHILD')),
              Center(child: Text('RIGHT CHILD')),
            ],
          ),
        ),
      );
    }

    await tester.pumpWidget(TabControllerFrame(
      builder: buildTabControllerFrame,
      length: tabs.length,
      initialIndex: 1,
    ));

    expect(find.text('LEFT'), findsOneWidget);
    expect(find.text('RIGHT'), findsOneWidget);
    expect(find.text('LEFT CHILD'), findsNothing);
    expect(find.text('RIGHT CHILD'), findsOneWidget);
    expect(tabController.index, 1);
    expect(tabController.previousIndex, 1);
    expect(tabController.indexIsChanging, false);
    expect(tabController.animation!.value, 1.0);
    expect(tabController.animation!.status, AnimationStatus.forward);

    tabController.index = 0;
    await tester.pump(const Duration(milliseconds: 500));
    await tester.pump(const Duration(milliseconds: 500));
    expect(find.text('LEFT CHILD'), findsOneWidget);
    expect(find.text('RIGHT CHILD'), findsNothing);

    tabController.index = 1;
    await tester.pump(const Duration(milliseconds: 500));
    await tester.pump(const Duration(milliseconds: 500));
    expect(find.text('LEFT CHILD'), findsNothing);
    expect(find.text('RIGHT CHILD'), findsOneWidget);
  });

  testWidgets('TabController listener resets index', (WidgetTester tester) async {
    // This is a regression test for the scenario brought up here
    // https://github.com/flutter/flutter/pull/7387#pullrequestreview-15630946

    final List<String> tabs = <String>['A', 'B', 'C'];
    late TabController tabController;

    Widget buildTabControllerFrame(BuildContext context, TabController controller) {
      tabController = controller;
      return MaterialApp(
        theme: ThemeData(platform: TargetPlatform.android),
        home: Scaffold(
          appBar: AppBar(
            title: const Text('tabs'),
            bottom: TabBar(
              controller: controller,
              tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            ),
          ),
          body: TabBarView(
            controller: controller,
            children: const <Widget>[
              Center(child: Text('CHILD A')),
              Center(child: Text('CHILD B')),
              Center(child: Text('CHILD C')),
            ],
          ),
        ),
      );
    }

    await tester.pumpWidget(TabControllerFrame(
      builder: buildTabControllerFrame,
      length: tabs.length,
    ));

    tabController.animation!.addListener(() {
      if (tabController.animation!.status == AnimationStatus.forward) {
        tabController.index = 2;
      }
      expect(tabController.indexIsChanging, true);
    });

    expect(tabController.index, 0);
    expect(tabController.indexIsChanging, false);

    tabController.animateTo(1, duration: const Duration(milliseconds: 200), curve: Curves.linear);
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 300));

    expect(tabController.index, 2);
    expect(tabController.indexIsChanging, false);
  });

  testWidgets('TabBar unselectedLabelColor control test', (WidgetTester tester) async {
    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: 2,
    );

    late Color firstColor;
    late Color secondColor;

    await tester.pumpWidget(
      boilerplate(
        child: TabBar(
          controller: controller,
          labelColor: Colors.green[500],
          unselectedLabelColor: Colors.blue[500],
          tabs: <Widget>[
            Builder(
              builder: (BuildContext context) {
                firstColor = IconTheme.of(context).color!;
                return const Text('First');
              },
            ),
            Builder(
              builder: (BuildContext context) {
                secondColor = IconTheme.of(context).color!;
                return const Text('Second');
              },
            ),
          ],
        ),
      ),
    );

    expect(firstColor, equals(Colors.green[500]));
    expect(secondColor, equals(Colors.blue[500]));
  });

  testWidgets('TabBarView page left and right test', (WidgetTester tester) async {
    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: 2,
    );

    await tester.pumpWidget(
      boilerplate(
        child: TabBarView(
          controller: controller,
          children: const <Widget>[ Text('First'), Text('Second') ],
        ),
      ),
    );

    expect(controller.index, equals(0));

    TestGesture gesture = await tester.startGesture(const Offset(100.0, 100.0));
    expect(controller.index, equals(0));

    // Drag to the left and right, by less than the TabBarView's width.
    // The selected index (controller.index) should not change.
    await gesture.moveBy(const Offset(-100.0, 0.0));
    await gesture.moveBy(const Offset(100.0, 0.0));
    expect(controller.index, equals(0));
    expect(find.text('First'), findsOneWidget);
    expect(find.text('Second'), findsNothing);

    // Drag more than the TabBarView's width to the right. This forces
    // the selected index to change to 1.
    await gesture.moveBy(const Offset(-500.0, 0.0));
    await gesture.up();
    await tester.pump(); // start the scroll animation
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(controller.index, equals(1));
    expect(find.text('First'), findsNothing);
    expect(find.text('Second'), findsOneWidget);

    gesture = await tester.startGesture(const Offset(100.0, 100.0));
    expect(controller.index, equals(1));

    // Drag to the left and right, by less than the TabBarView's width.
    // The selected index (controller.index) should not change.
    await gesture.moveBy(const Offset(-100.0, 0.0));
    await gesture.moveBy(const Offset(100.0, 0.0));
    expect(controller.index, equals(1));
    expect(find.text('First'), findsNothing);
    expect(find.text('Second'), findsOneWidget);

    // Drag more than the TabBarView's width to the left. This forces
    // the selected index to change back to 0.
    await gesture.moveBy(const Offset(500.0, 0.0));
    await gesture.up();
    await tester.pump(); // start the scroll animation
    await tester.pump(const Duration(seconds: 1)); // finish the scroll animation
    expect(controller.index, equals(0));
    expect(find.text('First'), findsOneWidget);
    expect(find.text('Second'), findsNothing);
  });

  testWidgets('TabBar animationDuration sets indicator animation duration', (WidgetTester tester) async {
    const Duration animationDuration = Duration(milliseconds: 100);
    final List<String> tabs = <String>['A', 'B', 'C'];

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: animationDuration));
    final TabController controller = DefaultTabController.of(tester.element(find.text('A')));

    await tester.tap(find.text('A'));
    await tester.pump();
    expect(controller.indexIsChanging, true);
    await tester.pump(const Duration(milliseconds: 50));
    await tester.pump(animationDuration);
    expect(controller.index, 0);
    expect(controller.previousIndex, 1);
    expect(controller.indexIsChanging, false);

    //Test when index diff is greater than 1
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: animationDuration));
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(controller.indexIsChanging, true);
    await tester.pump(const Duration(milliseconds: 50));
    await tester.pump(animationDuration);
    expect(controller.index, 2);
    expect(controller.previousIndex, 0);
    expect(controller.indexIsChanging, false);
  });

  testWidgets('TabBarView controller sets animation duration', (WidgetTester tester) async {
    const Duration animationDuration = Duration(milliseconds: 100);
    final List<String> tabs = <String>['A', 'B', 'C'];

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: tabs.length,
      animationDuration: animationDuration,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 400);
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(position.pixels, 400);
    await tester.pump(const Duration(milliseconds: 50));
    await tester.pump(animationDuration);
    expect(position.pixels, 800);
  });

  testWidgets('TabBarView animation can be interrupted', (WidgetTester tester) async {
    const Duration animationDuration = Duration(seconds: 2);
    final List<String> tabs = <String>['A', 'B', 'C'];

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      animationDuration: animationDuration,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 0);

    final PageView pageView = tester.widget<PageView>(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    expect(position.pixels, 0.0);

    await tester.tap(find.text('C'));
    await tester.pump(const Duration(milliseconds: 10)); // TODO(bleroux): find why this is needed.

    // Runs the animation for half of the animation duration.
    await tester.pump(const Duration(seconds: 1));

    // The position should be between page 1 and page 2.
    expect(position.pixels, greaterThan(400.0));
    expect(position.pixels, lessThan(800.0));

    // Switch to another tab before the end of the animation.
    await tester.tap(find.text('A'));
    await tester.pump(const Duration(milliseconds: 10)); // TODO(bleroux): find why this is needed.
    await tester.pump(animationDuration);
    expect(position.pixels, 0.0);

    await tester.pumpAndSettle(); // Finish the animation.
  });

  testWidgets('TabBarView viewportFraction sets PageView viewport fraction', (WidgetTester tester) async {
    const Duration animationDuration = Duration(milliseconds: 100);
    final List<String> tabs = <String>['A', 'B', 'C'];

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: tabs.length,
      animationDuration: animationDuration,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              viewportFraction: 0.8,
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;

    // The TabView was initialized with viewportFraction as 0.8
    // So it's expected the PageView inside would obtain the same viewportFraction
    expect(pageController.viewportFraction, 0.8);
  });

  testWidgets('TabBarView viewportFraction is 1 by default', (WidgetTester tester) async {
    const Duration animationDuration = Duration(milliseconds: 100);
    final List<String> tabs = <String>['A', 'B', 'C'];

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: tabs.length,
      animationDuration: animationDuration,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;

    // The TabView was initialized with default viewportFraction
    // So it's expected the PageView inside would obtain the value 1
    expect(pageController.viewportFraction, 1);
  });

  testWidgets('TabBarView has clipBehavior Clip.hardEdge by default', (WidgetTester tester) async {
    final List<Widget> tabs = <Widget>[const Text('First'), const Text('Second')];

    Widget builder() {
      return boilerplate(
        child: DefaultTabController(
          length: tabs.length,
          child: TabBarView(
            children: tabs,
          ),
        ),
      );
    }

    await tester.pumpWidget(builder());
    final TabBarView tabBarView = tester.widget(find.byType(TabBarView));
    expect(tabBarView.clipBehavior, Clip.hardEdge);
  });

  testWidgets('TabBarView sets clipBehavior correctly', (WidgetTester tester) async {
    final List<Widget> tabs = <Widget>[const Text('First'), const Text('Second')];

    Widget builder() {
      return boilerplate(
        child: DefaultTabController(
          length: tabs.length,
          child: TabBarView(
            clipBehavior: Clip.none,
            children: tabs,
          ),
        ),
      );
    }

    await tester.pumpWidget(builder());
    final PageView pageView = tester.widget(find.byType(PageView));
    expect(pageView.clipBehavior, Clip.none);
  });

  testWidgets('TabBar tap skips indicator animation when disabled in controller', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B'];

    const Color indicatorColor = Color(0xFFFF0000);
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'A', indicatorColor: indicatorColor, animationDuration: Duration.zero));

    final RenderBox box = tester.renderObject(find.byType(TabBar));
    final TabIndicatorRecordingCanvas canvas = TabIndicatorRecordingCanvas(indicatorColor);
    final TestRecordingPaintingContext context = TestRecordingPaintingContext(canvas);

    box.paint(context, Offset.zero);
    final Rect indicatorRect0 = canvas.indicatorRect;
    expect(indicatorRect0.left, 0.0);
    expect(indicatorRect0.width, 400.0);
    expect(indicatorRect0.height, 2.0);

    await tester.tap(find.text('B'));
    await tester.pump();
    box.paint(context, Offset.zero);
    final Rect indicatorRect2 = canvas.indicatorRect;
    expect(indicatorRect2.left, 400.0);
    expect(indicatorRect2.width, 400.0);
    expect(indicatorRect2.height, 2.0);
  });

  testWidgets('TabBar tap changes index instantly when animation is disabled in controller', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: Duration.zero));
    final TabController controller = DefaultTabController.of(tester.element(find.text('A')));

    await tester.tap(find.text('A'));
    await tester.pump();
    expect(controller.index, 0);
    expect(controller.previousIndex, 1);
    expect(controller.indexIsChanging, false);

    //Test when index diff is greater than 1
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: Duration.zero));
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(controller.index, 2);
    expect(controller.previousIndex, 0);
    expect(controller.indexIsChanging, false);
  });

  testWidgets('Scrollable TabBar does not have overscroll indicator', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];

    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'A', isScrollable: true));
    expect(find.byType(GlowingOverscrollIndicator), findsNothing);
  });

  testWidgets('TabBar should not throw when animation is disabled in controller', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/102600
    final List<String> tabs = <String>['A'];

    Widget buildWithTabBarView() {
      return boilerplate(
        child: DefaultTabController(
          animationDuration: Duration.zero,
          length: tabs.length,
          child: Column(
            children: <Widget>[
              TabBar(
                tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
                isScrollable: true,
              ),
              Flexible(
                child: TabBarView(
                  children: List<Widget>.generate(
                    tabs.length,
                    (int index) => Text('Tab $index'),
                  ),
                ),
              ),
            ],
          ),
        ),
      );
    }

    await tester.pumpWidget(buildWithTabBarView());
    TabController controller = DefaultTabController.of(tester.element(find.text('A')));
    expect(controller.index, 0);

    tabs.add('B');
    await tester.pumpWidget(buildWithTabBarView());
    tabs.add('C');
    await tester.pumpWidget(buildWithTabBarView());
    await tester.tap(find.text('C'));
    await tester.pumpAndSettle();
    controller = DefaultTabController.of(tester.element(find.text('A')));
    expect(controller.index, 2);

    expect(tester.takeException(), isNull);
  });

  testWidgets('TabBarView skips animation when disabled in controller', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: tabs.length,
      animationDuration: Duration.zero,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 400);
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(position.pixels, 800);
  });

  testWidgets('TabBarView skips animation when disabled in controller - skip tabs', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B', 'C'];
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      animationDuration: Duration.zero,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 0);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 0);
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(position.pixels, 800);
  });

  testWidgets('TabBarView skips animation when disabled in controller - skip tabs twice', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/110970
    final List<String> tabs = <String>['A', 'B', 'C'];
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      animationDuration: Duration.zero,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 0);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 0);
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(position.pixels, 800);

    await tester.tap(find.text('A'));
    await tester.pump();
    expect(position.pixels, 0);
  });

  testWidgets('TabBarView skips animation when disabled in controller - skip tabs followed by single tab navigation', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/110970
    final List<String> tabs = <String>['A', 'B', 'C'];
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      animationDuration: Duration.zero,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 0);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 0);
    await tester.tap(find.text('C'));
    await tester.pump();
    expect(position.pixels, 800);

    await tester.tap(find.text('B'));
    await tester.pump();
    expect(position.pixels, 400);

    await tester.tap(find.text('A'));
    await tester.pump();
    expect(position.pixels, 0);
  });

  testWidgets('TabBarView skips animation when disabled in controller - two tabs', (WidgetTester tester) async {
    final List<String> tabs = <String>['A', 'B'];
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      animationDuration: Duration.zero,
    );
    await tester.pumpWidget(boilerplate(
      child: Column(
        children: <Widget>[
          TabBar(
            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
            controller: tabController,
          ),
          SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
              ],
            ),
          ),
        ],
      ),
    ));

    expect(tabController.index, 0);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.
    expect(position.pixels, 0);
    await tester.tap(find.text('B'));
    await tester.pump();
    expect(position.pixels, 400);
  });

  testWidgets('TabBar tap animates the selection indicator', (WidgetTester tester) async {
    // This is a regression test for https://github.com/flutter/flutter/issues/7479

    final List<String> tabs = <String>['A', 'B'];

    const Color indicatorColor = Color(0xFFFF0000);
    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'A', indicatorColor: indicatorColor));

    final RenderBox box = tester.renderObject(find.byType(TabBar));
    final TabIndicatorRecordingCanvas canvas = TabIndicatorRecordingCanvas(indicatorColor);
    final TestRecordingPaintingContext context = TestRecordingPaintingContext(canvas);

    box.paint(context, Offset.zero);
    final Rect indicatorRect0 = canvas.indicatorRect;
    expect(indicatorRect0.left, 0.0);
    expect(indicatorRect0.width, 400.0);
    expect(indicatorRect0.height, 2.0);

    await tester.tap(find.text('B'));
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));
    box.paint(context, Offset.zero);
    final Rect indicatorRect1 = canvas.indicatorRect;
    expect(indicatorRect1.left, greaterThan(indicatorRect0.left));
    expect(indicatorRect1.right, lessThan(800.0));
    expect(indicatorRect1.height, 2.0);

    await tester.pump(const Duration(milliseconds: 300));
    box.paint(context, Offset.zero);
    final Rect indicatorRect2 = canvas.indicatorRect;
    expect(indicatorRect2.left, 400.0);
    expect(indicatorRect2.width, 400.0);
    expect(indicatorRect2.height, 2.0);
  });

  testWidgets('TabBarView child disposed during animation', (WidgetTester tester) async {
    // This is a regression test for this patch:
    // https://github.com/flutter/flutter/pull/9015

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: 2,
    );

    Widget buildFrame() {
      return boilerplate(
        child: TabBar(
          key: UniqueKey(),
          controller: controller,
          tabs: const <Widget>[ Text('A'), Text('B') ],
        ),
      );
    }

    await tester.pumpWidget(buildFrame());

    // The original TabBar will be disposed. The controller should no
    // longer have any listeners from the original TabBar.
    await tester.pumpWidget(buildFrame());

    controller.index = 1;
    await tester.pump(const Duration(milliseconds: 300));
  });


  group('TabBarView children updated', () {

    Widget buildFrameWithMarker(List<String> log, String marker) {
      return MaterialApp(
        home: DefaultTabController(
          animationDuration: const Duration(seconds: 1),
          length: 3,
          child: Scaffold(
            appBar: AppBar(
              bottom: const TabBar(
                tabs: <Widget>[
                  Tab(text: 'A'),
                  Tab(text: 'B'),
                  Tab(text: 'C'),
                ],
              ),
              title: const Text('Tabs Test'),
            ),
            body: TabBarView(
              children: <Widget>[
                TabBody(index: 0, log: log, marker: marker),
                TabBody(index: 1, log: log, marker: marker),
                TabBody(index: 2, log: log, marker: marker),
              ],
            ),
          ),
        ),
      );
    }

    testWidgets('TabBarView children can be updated during animation to an adjacent tab', (WidgetTester tester) async {
      // Regression test for https://github.com/flutter/flutter/issues/107399
      final List<String> log = <String>[];

      const String initialMarker = 'before';
      await tester.pumpWidget(buildFrameWithMarker(log, initialMarker));
      expect(log, <String>['init: 0']);
      expect(find.text('0-$initialMarker'), findsOneWidget);

      // Select the second tab and wait until the transition starts
      await tester.tap(find.text('B'));
      await tester.pump(const Duration(milliseconds: 100));

      // Check that both TabBody's are instantiated while the transition is animating
      await tester.pump(const Duration(milliseconds: 400));
      expect(log, <String>['init: 0', 'init: 1']);

      // Update the TabBody's states while the transition is animating
      const String updatedMarker = 'after';
      await tester.pumpWidget(buildFrameWithMarker(log, updatedMarker));

      // Wait until the transition ends
      await tester.pumpAndSettle();

      // The TabBody state of the second TabBar should have been updated
      expect(find.text('1-$initialMarker'), findsNothing);
      expect(find.text('1-$updatedMarker'), findsOneWidget);
    });

    testWidgets('TabBarView children can be updated during animation to a non adjacent tab', (WidgetTester tester) async {
      final List<String> log = <String>[];

      const String initialMarker = 'before';
      await tester.pumpWidget(buildFrameWithMarker(log, initialMarker));
      expect(log, <String>['init: 0']);
      expect(find.text('0-$initialMarker'), findsOneWidget);

      // Select the third tab and wait until the transition starts
      await tester.tap(find.text('C'));
      await tester.pump(const Duration(milliseconds: 100));

      // Check that both TabBody's are instantiated while the transition is animating
      await tester.pump(const Duration(milliseconds: 400));
      expect(log, <String>['init: 0', 'init: 2']);

      // Update the TabBody's states while the transition is animating
      const String updatedMarker = 'after';
      await tester.pumpWidget(buildFrameWithMarker(log, updatedMarker));

      // Wait until the transition ends
      await tester.pumpAndSettle();

      // The TabBody state of the third TabBar should have been updated
      expect(find.text('2-$initialMarker'), findsNothing);
      expect(find.text('2-$updatedMarker'), findsOneWidget);
    });
  });

  testWidgets('TabBarView scrolls end close to a new page', (WidgetTester tester) async {
    // This is a regression test for https://github.com/flutter/flutter/issues/9375

    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: 3,
    );

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: SizedBox.expand(
        child: Center(
          child: SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ),
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.

    expect(position.pixels, 400.0);

    // Not close enough to switch to page 2
    pageController.jumpTo(500.0);
    expect(tabController.index, 1);

    // Close enough to switch to page 2
    pageController.jumpTo(700.0);
    expect(tabController.index, 2);

    // Same behavior going left: not left enough to get to page 0
    pageController.jumpTo(300.0);
    expect(tabController.index, 1);

    // Left enough to get to page 0
    pageController.jumpTo(100.0);
    expect(tabController.index, 0);
  });

  testWidgets('Can switch to non-neighboring tab in nested TabBarView without crashing', (WidgetTester tester) async {
    // This is a regression test for https://github.com/flutter/flutter/issues/18756
    final TabController mainTabController = TabController(length: 4, vsync: const TestVSync());
    final TabController nestedTabController = TabController(length: 2, vsync: const TestVSync());

    await tester.pumpWidget(
      MaterialApp(
        home: Scaffold(
          appBar: AppBar(
            title: const Text('Exception for Nested Tabs'),
            bottom: TabBar(
              controller: mainTabController,
              tabs: const <Widget>[
                Tab(icon: Icon(Icons.add), text: 'A'),
                Tab(icon: Icon(Icons.add), text: 'B'),
                Tab(icon: Icon(Icons.add), text: 'C'),
                Tab(icon: Icon(Icons.add), text: 'D'),
              ],
            ),
          ),
          body: TabBarView(
            controller: mainTabController,
            children: <Widget>[
              Container(color: Colors.red),
              _NestedTabBarContainer(tabController: nestedTabController),
              Container(color: Colors.green),
              Container(color: Colors.indigo),
            ],
          ),
        ),
      ),
    );

    // expect first tab to be selected
    expect(mainTabController.index, 0);

    // tap on third tab
    await tester.tap(find.text('C'));
    await tester.pumpAndSettle();

    // expect third tab to be selected without exceptions
    expect(mainTabController.index, 2);
  });

  testWidgets('TabBarView can warp when child is kept alive and contains ink', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/57662.
    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: 3,
    );

    await tester.pumpWidget(
      boilerplate(
        child: TabBarView(
          controller: controller,
          children: const <Widget>[
            Text('Page 1'),
            Text('Page 2'),
            KeepAliveInk('Page 3'),
          ],
        ),
      ),
    );

    expect(controller.index, equals(0));
    expect(find.text('Page 1'), findsOneWidget);
    expect(find.text('Page 3'), findsNothing);

    controller.index = 2;
    await tester.pumpAndSettle();
    expect(find.text('Page 1'), findsNothing);
    expect(find.text('Page 3'), findsOneWidget);

    controller.index = 0;
    await tester.pumpAndSettle();
    expect(find.text('Page 1'), findsOneWidget);
    expect(find.text('Page 3'), findsNothing);

    expect(tester.takeException(), isNull);
  });

  testWidgets('TabBarView scrolls end close to a new page with custom physics', (WidgetTester tester) async {
    final TabController tabController = TabController(
      vsync: const TestVSync(),
      initialIndex: 1,
      length: 3,
    );

    await tester.pumpWidget(Directionality(
      textDirection: TextDirection.ltr,
      child: SizedBox.expand(
        child: Center(
          child: SizedBox(
            width: 400.0,
            height: 400.0,
            child: TabBarView(
              controller: tabController,
              physics: const TestScrollPhysics(),
              children: const <Widget>[
                Center(child: Text('0')),
                Center(child: Text('1')),
                Center(child: Text('2')),
              ],
            ),
          ),
        ),
      ),
    ));

    expect(tabController.index, 1);

    final PageView pageView = tester.widget(find.byType(PageView));
    final PageController pageController = pageView.controller;
    final ScrollPosition position = pageController.position;

    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
    // page 1 is at 400.0, page 2 is at 800.0.

    expect(position.pixels, 400.0);

    // Not close enough to switch to page 2
    pageController.jumpTo(500.0);
    expect(tabController.index, 1);

    // Close enough to switch to page 2
    pageController.jumpTo(700.0);
    expect(tabController.index, 2);

    // Same behavior going left: not left enough to get to page 0
    pageController.jumpTo(300.0);
    expect(tabController.index, 1);

    // Left enough to get to page 0
    pageController.jumpTo(100.0);
    expect(tabController.index, 0);
  });

  testWidgets('TabBar accepts custom physics', (WidgetTester tester) async {
    final List<Tab> tabs = List<Tab>.generate(20, (int index) {
      return Tab(text: 'TAB #$index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      initialIndex: tabs.length - 1,
    );

    await tester.pumpWidget(
      boilerplate(
        child: TabBar(
          isScrollable: true,
          controller: controller,
          tabs: tabs,
          physics: const TestScrollPhysics(),
        ),
      ),
    );

    final TabBar tabBar = tester.widget(find.byType(TabBar));
    final double position = tabBar.physics!.applyPhysicsToUserOffset(MockScrollMetrics(), 10);

    expect(position, equals(20));
  });

  testWidgets('Scrollable TabBar with a non-zero TabController initialIndex', (WidgetTester tester) async {
    // This is a regression test for https://github.com/flutter/flutter/issues/9374

    final List<Tab> tabs = List<Tab>.generate(20, (int index) {
      return Tab(text: 'TAB #$index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
      initialIndex: tabs.length - 1,
    );

    await tester.pumpWidget(
      boilerplate(
        child: TabBar(
          isScrollable: true,
          controller: controller,
          tabs: tabs,
        ),
      ),
    );

    // The initialIndex tab should be visible and right justified
    expect(find.text('TAB #19'), findsOneWidget);

    // Tabs have a minimum width of 72.0 and 'TAB #19' is wider than
    // that. Tabs are padded horizontally with kTabLabelPadding.
    final double tabRight = 800.0 - kTabLabelPadding.right;

    expect(tester.getTopRight(find.widgetWithText(Tab, 'TAB #19')).dx, tabRight);
  });

  testWidgets('TabBar with indicatorWeight, indicatorPadding (LTR)', (WidgetTester tester) async {
    const Color indicatorColor = Color(0xFF00FF00);
    const double indicatorWeight = 8.0;
    const double padLeft = 8.0;
    const double padRight = 4.0;

    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicatorWeight: indicatorWeight,
            indicatorColor: indicatorColor,
            indicatorPadding: const EdgeInsets.only(left: padLeft, right: padRight),
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 54.0); // 54 = _kTabHeight(46) + indicatorWeight(8.0)

    const double indicatorY = 54.0 - indicatorWeight / 2.0;
    double indicatorLeft = padLeft + indicatorWeight / 2.0;
    double indicatorRight = 200.0 - (padRight + indicatorWeight / 2.0);

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));

    // Select tab 3
    controller.index = 3;
    await tester.pumpAndSettle();

    indicatorLeft = 600.0 + padLeft + indicatorWeight / 2.0;
    indicatorRight = 800.0 - (padRight + indicatorWeight / 2.0);

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));
  });

  testWidgets('TabBar with indicatorWeight, indicatorPadding (RTL)', (WidgetTester tester) async {
    const Color indicatorColor = Color(0xFF00FF00);
    const double indicatorWeight = 8.0;
    const double padLeft = 8.0;
    const double padRight = 4.0;

    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        textDirection: TextDirection.rtl,
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicatorWeight: indicatorWeight,
            indicatorColor: indicatorColor,
            indicatorPadding: const EdgeInsets.only(left: padLeft, right: padRight),
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 54.0); // 54 = _kTabHeight(46) + indicatorWeight(8.0)
    expect(tabBarBox.size.width, 800.0);

    const double indicatorY = 54.0 - indicatorWeight / 2.0;
    double indicatorLeft = 600.0 + padLeft + indicatorWeight / 2.0;
    double indicatorRight = 800.0 - padRight - indicatorWeight / 2.0;

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));

    // Select tab 3
    controller.index = 3;
    await tester.pumpAndSettle();

    indicatorLeft = padLeft + indicatorWeight / 2.0;
    indicatorRight = 200.0 - padRight -  indicatorWeight / 2.0;

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));
  });

  testWidgets('TabBar changes indicator attributes', (WidgetTester tester) async {
    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    Color indicatorColor = const Color(0xFF00FF00);
    double indicatorWeight = 8.0;
    double padLeft = 8.0;
    double padRight = 4.0;

    Widget buildFrame() {
      return boilerplate(
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicatorWeight: indicatorWeight,
            indicatorColor: indicatorColor,
            indicatorPadding: EdgeInsets.only(left: padLeft, right: padRight),
            controller: controller,
            tabs: tabs,
          ),
        ),
      );
    }

    await tester.pumpWidget(buildFrame());

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 54.0); // 54 = _kTabHeight(46) + indicatorWeight(8.0)

    double indicatorY = 54.0 - indicatorWeight / 2.0;
    double indicatorLeft = padLeft + indicatorWeight / 2.0;
    double indicatorRight = 200.0 - (padRight + indicatorWeight / 2.0);

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));

    indicatorColor = const Color(0xFF0000FF);
    indicatorWeight = 4.0;
    padLeft = 4.0;
    padRight = 8.0;

    await tester.pumpWidget(buildFrame());

    expect(tabBarBox.size.height, 50.0); // 54 = _kTabHeight(46) + indicatorWeight(4.0)

    indicatorY = 50.0 - indicatorWeight / 2.0;
    indicatorLeft = padLeft + indicatorWeight / 2.0;
    indicatorRight = 200.0 - (padRight + indicatorWeight / 2.0);

    expect(tabBarBox, paints..line(
      color: indicatorColor,
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));
  });

  testWidgets('TabBar with directional indicatorPadding (LTR)', (WidgetTester tester) async {
    final List<Widget> tabs = <Widget>[
      SizedBox(key: UniqueKey(), width: 130.0, height: 30.0),
      SizedBox(key: UniqueKey(), width: 140.0, height: 40.0),
      SizedBox(key: UniqueKey(), width: 150.0, height: 50.0),
    ];

    const double indicatorWeight = 2.0; // the default

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicatorPadding: const EdgeInsetsDirectional.only(start: 100.0),
            isScrollable: true,
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    const double tabBarHeight = 50.0 + indicatorWeight;  // 50 = max tab height
    expect(tabBarBox.size.height, tabBarHeight);

    // Tab0 width = 130, height = 30
    double tabLeft = kTabLabelPadding.left;
    double tabRight = tabLeft + 130.0;
    double tabTop = (tabBarHeight - indicatorWeight - 30.0) / 2.0;
    double tabBottom = tabTop + 30.0;
    Rect tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[0].key!)), tabRect);


    // Tab1 width = 140, height = 40
    tabLeft = tabRight + kTabLabelPadding.right + kTabLabelPadding.left;
    tabRight = tabLeft + 140.0;
    tabTop = (tabBarHeight - indicatorWeight - 40.0) / 2.0;
    tabBottom = tabTop + 40.0;
    tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[1].key!)), tabRect);


    // Tab2 width = 150, height = 50
    tabLeft = tabRight + kTabLabelPadding.right + kTabLabelPadding.left;
    tabRight = tabLeft + 150.0;
    tabTop = (tabBarHeight - indicatorWeight - 50.0) / 2.0;
    tabBottom = tabTop + 50.0;
    tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[2].key!)), tabRect);

    // Tab 0 selected, indicator padding resolves to left: 100.0
    const double indicatorLeft = 100.0 + indicatorWeight / 2.0;
    final double indicatorRight = 130.0 + kTabLabelPadding.horizontal - indicatorWeight / 2.0;
    final double indicatorY = tabBottom + indicatorWeight / 2.0;
    expect(tabBarBox, paints..line(
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));
  });

  testWidgets('TabBar with directional indicatorPadding (RTL)', (WidgetTester tester) async {
    final List<Widget> tabs = <Widget>[
      SizedBox(key: UniqueKey(), width: 130.0, height: 30.0),
      SizedBox(key: UniqueKey(), width: 140.0, height: 40.0),
      SizedBox(key: UniqueKey(), width: 150.0, height: 50.0),
    ];

    const double indicatorWeight = 2.0; // the default

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        textDirection: TextDirection.rtl,
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicatorPadding: const EdgeInsetsDirectional.only(start: 100.0),
            isScrollable: true,
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox = tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    const double tabBarHeight = 50.0 + indicatorWeight;  // 50 = max tab height
    expect(tabBarBox.size.height, tabBarHeight);

    // Tab2 width = 150, height = 50
    double tabLeft = kTabLabelPadding.left;
    double tabRight = tabLeft + 150.0;
    double tabTop = (tabBarHeight - indicatorWeight - 50.0) / 2.0;
    double tabBottom = tabTop + 50.0;
    Rect tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[2].key!)), tabRect);

    // Tab1 width = 140, height = 40
    tabLeft = tabRight + kTabLabelPadding.right + kTabLabelPadding.left;
    tabRight = tabLeft + 140.0;
    tabTop = (tabBarHeight - indicatorWeight - 40.0) / 2.0;
    tabBottom = tabTop + 40.0;
    tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[1].key!)), tabRect);

    // Tab0 width = 130, height = 30
    tabLeft = tabRight + kTabLabelPadding.right + kTabLabelPadding.left;
    tabRight = tabLeft + 130.0;
    tabTop = (tabBarHeight - indicatorWeight - 30.0) / 2.0;
    tabBottom = tabTop + 30.0;
    tabRect = Rect.fromLTRB(tabLeft, tabTop, tabRight, tabBottom);
    expect(tester.getRect(find.byKey(tabs[0].key!)), tabRect);

    // Tab 0 selected, indicator padding resolves to right: 100.0
    final double indicatorLeft = tabLeft - kTabLabelPadding.left + indicatorWeight / 2.0;
    final double indicatorRight = tabRight + kTabLabelPadding.left - indicatorWeight / 2.0 - 100.0;
    const double indicatorY = 50.0 + indicatorWeight / 2.0;
    expect(tabBarBox, paints..line(
      strokeWidth: indicatorWeight,
      p1: Offset(indicatorLeft, indicatorY),
      p2: Offset(indicatorRight, indicatorY),
    ));
  });

  testWidgets('TabBar with custom indicator and indicatorPadding(LTR)', (WidgetTester tester) async {
    const Color indicatorColor = Color(0xFF00FF00);
    const double padTop = 10.0;
    const double padBottom = 12.0;
    const double padLeft = 8.0;
    const double padRight = 4.0;
    const Decoration indicator = BoxDecoration(color: indicatorColor);

    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicator: indicator,
            indicatorPadding:
            const EdgeInsets.fromLTRB(padLeft, padTop, padRight, padBottom),
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox =
    tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 48.0);
    // 48 = _kTabHeight(46) + indicatorWeight(2.0) ~default

    const double indicatorBottom = 48.0 - padBottom;
    const double indicatorTop = padTop;
    double indicatorLeft = padLeft;
    double indicatorRight = 200.0 - padRight;

    expect(tabBarBox, paints..rect(
      rect: Rect.fromLTRB(
        indicatorLeft,
        indicatorTop,
        indicatorRight,
        indicatorBottom,
      ),
      color: indicatorColor,
    ));

    // Select tab 3
    controller.index = 3;
    await tester.pumpAndSettle();

    indicatorLeft = 600.0 + padLeft;
    indicatorRight = 800.0 - padRight;

    expect(tabBarBox, paints..rect(
      rect: Rect.fromLTRB(
        indicatorLeft,
        indicatorTop,
        indicatorRight,
        indicatorBottom,
      ),
      color: indicatorColor,
    ));
  });

  testWidgets('TabBar with custom indicator and indicatorPadding (RTL)', (WidgetTester tester) async {
    const Color indicatorColor = Color(0xFF00FF00);
    const double padTop = 10.0;
    const double padBottom = 12.0;
    const double padLeft = 8.0;
    const double padRight = 4.0;
    const Decoration indicator = BoxDecoration(color: indicatorColor);

    final List<Widget> tabs = List<Widget>.generate(4, (int index) {
      return Tab(text: 'Tab $index');
    });

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        textDirection: TextDirection.rtl,
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
          indicator: indicator,
          indicatorPadding: const EdgeInsets.fromLTRB(padLeft, padTop, padRight, padBottom),
          controller: controller,
          tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarBox =
    tester.firstRenderObject<RenderBox>(find.byType(TabBar));
    expect(tabBarBox.size.height, 48.0);
    // 48 = _kTabHeight(46) + indicatorWeight(2.0) ~default
    expect(tabBarBox.size.width, 800.0);
    const double indicatorBottom = 48.0 - padBottom;
    const double indicatorTop = padTop;
    double indicatorLeft = 600.0 + padLeft;
    double indicatorRight = 800.0 - padRight;

    expect(tabBarBox, paints..rect(
      rect: Rect.fromLTRB(
        indicatorLeft,
        indicatorTop,
        indicatorRight,
        indicatorBottom,
      ),
      color: indicatorColor,
    ));

    // Select tab 3
    controller.index = 3;
    await tester.pumpAndSettle();

    indicatorLeft = padLeft;
    indicatorRight = 200.0 - padRight;

    expect(tabBarBox,paints..rect(
      rect: Rect.fromLTRB(
        indicatorLeft,
        indicatorTop,
        indicatorRight,
        indicatorBottom,
      ),
      color: indicatorColor,
    ));
  });

  testWidgets('TabBar with custom indicator - directional indicatorPadding (LTR)', (WidgetTester tester) async {
    final List<Widget > tabs = <Widget>[
      SizedBox(key: UniqueKey(), width: 130.0, height: 30.0),
      SizedBox(key: UniqueKey(), width: 140.0, height: 40.0),
      SizedBox(key: UniqueKey(), width: 150.0, height: 50.0),
    ];
    const Color indicatorColor = Color(0xFF00FF00);
    const double padTop = 10.0;
    const double padBottom = 12.0;
    const double padStart = 8.0;
    const double padEnd = 4.0;
    const Decoration indicator = BoxDecoration(color: indicatorColor);
    const double indicatorWeight = 2.0; // the default

    final TabController controller = TabController(
      vsync: const TestVSync(),
      length: tabs.length,
    );

    await tester.pumpWidget(
      boilerplate(
        child: Container(
          alignment: Alignment.topLeft,
          child: TabBar(
            indicator: indicator,
            indicatorPadding: const EdgeInsetsDirectional.fromSTEB(padStart, padTop, padEnd, padBottom),
            isScrollable: true,
            controller: controller,
            tabs: tabs,
          ),
        ),
      ),
    );

    final RenderBox tabBarB