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ksokolovskyiksokolovskyi
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Add test for tab_controller.1.dart API example. (#148189)
This PR contributes to flutter/flutter#130459 ### Description - Updates `examples/api/lib/material/tab_controller/tab_controller.1.dart` to properly remove the listener from the `TabController` - Adds tests for `examples/api/lib/material/tab_controller/tab_controller.1.dart`
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-25
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3 files changed

+184
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lines changed

‎dev/bots/check_code_samples.dart‎

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@@ -346,7 +346,6 @@ final Set<String> _knownMissingTests = <String>{
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'examples/api/test/material/search_anchor/search_anchor.1_test.dart',
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'examples/api/test/material/search_anchor/search_anchor.2_test.dart',
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'examples/api/test/material/about/about_list_tile.0_test.dart',
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'examples/api/test/material/tab_controller/tab_controller.1_test.dart',
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'examples/api/test/material/selection_area/selection_area.0_test.dart',
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'examples/api/test/material/scaffold/scaffold.end_drawer.0_test.dart',
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'examples/api/test/material/scaffold/scaffold.drawer.0_test.dart',

‎examples/api/lib/material/tab_controller/tab_controller.1.dart‎

Lines changed: 88 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -11,42 +11,39 @@ void main() => runApp(const TabControllerExampleApp());
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class TabControllerExampleApp extends StatelessWidget {
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const TabControllerExampleApp({super.key});
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static const List<Tab> tabs = <Tab>[
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Tab(text: 'Zeroth'),
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Tab(text: 'First'),
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Tab(text: 'Second'),
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];
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@override
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Widget build(BuildContext context) {
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return const MaterialApp(
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home: TabControllerExample(),
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home: TabControllerExample(tabs: tabs),
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);
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}
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}
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const List<Tab> tabs = <Tab>[
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Tab(text: 'Zeroth'),
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Tab(text: 'First'),
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Tab(text: 'Second'),
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];
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class TabControllerExample extends StatelessWidget {
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const TabControllerExample({super.key});
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const TabControllerExample({
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required this.tabs,
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super.key,
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});
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final List<Tab> tabs;
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@override
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Widget build(BuildContext context) {
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return DefaultTabController(
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length: tabs.length,
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// The Builder widget is used to have a different BuildContext to access
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// closest DefaultTabController.
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child: Builder(builder: (BuildContext context) {
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final TabController tabController = DefaultTabController.of(context);
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tabController.addListener(() {
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if (!tabController.indexIsChanging) {
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// Your code goes here.
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// To get index of current tab use tabController.index
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}
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});
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return Scaffold(
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child: DefaultTabControllerListener(
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onTabChanged: (int index) {
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debugPrint('tab changed: $index');
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},
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child: Scaffold(
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appBar: AppBar(
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bottom: const TabBar(
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tabs: tabs,
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),
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bottom: TabBar(tabs: tabs),
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),
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body: TabBarView(
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children: tabs.map((Tab tab) {
@@ -58,8 +55,75 @@ class TabControllerExample extends StatelessWidget {
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);
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}).toList(),
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),
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);
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}),
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),
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),
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);
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}
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}
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class DefaultTabControllerListener extends StatefulWidget {
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const DefaultTabControllerListener({
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required this.onTabChanged,
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required this.child,
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super.key,
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});
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final ValueChanged<int> onTabChanged;
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final Widget child;
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@override
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State<DefaultTabControllerListener> createState() =>
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_DefaultTabControllerListenerState();
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}
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class _DefaultTabControllerListenerState
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extends State<DefaultTabControllerListener> {
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TabController? _controller;
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@override
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void didChangeDependencies() {
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super.didChangeDependencies();
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final TabController? defaultTabController =
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DefaultTabController.maybeOf(context);
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assert(() {
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if (defaultTabController == null) {
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throw FlutterError(
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'No DefaultTabController for ${widget.runtimeType}.\n'
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'When creating a ${widget.runtimeType}, you must ensure that there '
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'is a DefaultTabController above the ${widget.runtimeType}.',
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);
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}
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return true;
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}());
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if (defaultTabController != _controller) {
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_controller?.removeListener(_listener);
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_controller = defaultTabController;
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_controller?.addListener(_listener);
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}
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}
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void _listener() {
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final TabController? controller = _controller;
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if (controller == null || controller.indexIsChanging) {
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return;
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}
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widget.onTabChanged(controller.index);
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}
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@override
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void dispose() {
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_controller?.removeListener(_listener);
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super.dispose();
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}
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@override
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Widget build(BuildContext context) {
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return widget.child;
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}
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}

‎examples/api/test/material/tab_controller/tab_controller.1_test.dart‎

Lines changed: 96 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,96 @@
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// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/foundation.dart';
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import 'package:flutter/material.dart';
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import 'package:flutter_api_samples/material/tab_controller/tab_controller.1.dart'
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as example;
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import 'package:flutter_test/flutter_test.dart';
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void main() {
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testWidgets('Verify first tab is selected by default', (WidgetTester tester) async {
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await tester.pumpWidget(
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const example.TabControllerExampleApp(),
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);
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final Tab firstTab = example.TabControllerExampleApp.tabs.first;
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expect(
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find.descendant(
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of: find.byType(TabBarView),
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matching: find.text('${firstTab.text} Tab'),
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),
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findsOneWidget,
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);
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});
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testWidgets('Verify tabs can be changed', (WidgetTester tester) async {
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final List<String?> log = <String?>[];
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final DebugPrintCallback originalDebugPrint = debugPrint;
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debugPrint = (String? message, {int? wrapWidth}) {
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log.add(message);
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};
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await tester.pumpWidget(
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const example.TabControllerExampleApp(),
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);
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const List<Tab> tabs = example.TabControllerExampleApp.tabs;
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final List<Tab> tabsTraversalOrder = <Tab>[];
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// The traverse order is from the second tab from the start to the last,
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// and then from the second tab from the end to the first.
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tabsTraversalOrder.addAll(tabs.skip(1));
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tabsTraversalOrder.addAll(tabs.reversed.skip(1));
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for (final Tab tab in tabsTraversalOrder) {
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// Tap on the TabBar's tab to select it.
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await tester.tap(find.descendant(
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of: find.byType(TabBar),
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matching: find.text(tab.text!),
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));
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await tester.pumpAndSettle();
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expect(
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find.descendant(
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of: find.byType(TabBarView),
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matching: find.text('${tab.text} Tab'),
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),
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findsOneWidget,
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);
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expect(log.length, equals(1));
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expect(log.last, equals('tab changed: ${tabs.indexOf(tab)}'));
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log.clear();
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}
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debugPrint = originalDebugPrint;
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});
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testWidgets('DefaultTabControllerListener throws when no DefaultTabController above', (WidgetTester tester) async {
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await tester.pumpWidget(
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example.DefaultTabControllerListener(
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onTabChanged: (_) {},
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child: const SizedBox.shrink(),
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),
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);
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final dynamic exception = tester.takeException();
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expect(exception, isFlutterError);
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final FlutterError error = exception as FlutterError;
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expect(
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error.toStringDeep(),
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equalsIgnoringHashCodes(
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'FlutterError\n'
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' No DefaultTabController for DefaultTabControllerListener.\n'
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' When creating a DefaultTabControllerListener, you must ensure\n'
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' that there is a DefaultTabController above the\n'
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' DefaultTabControllerListener.\n',
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),
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);
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});
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}

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