如何在Flutter中通过Navigator测试导航-Java 学习之路

比方说，我使用 WidgetTester 对Flutter中的屏幕进行了测试 . 有一个按钮，通过 Navigator 执行导航 . 我想测试该按钮的行为 .

Widget/Screen

class MyScreen extends StatefulWidget {

  MyScreen({Key key}) : super(key: key);

  @override
  _MyScreenState createState() => _MyScreenScreenState();
}

class _MyScreenState extends State<MyScreen> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child: RaisedButton(
                onPressed: () {
                    Navigator.of(context).pushNamed("/nextscreen");
                },
                child: Text(Strings.traktTvUrl)
            )
        )
    );
  }

}

Test

void main() {

  testWidgets('Button is present and triggers navigation after tapped',
      (WidgetTester tester) async {
    await tester.pumpWidget(MaterialApp(home: MyScreen()));
    expect(find.byType(RaisedButton), findsOneWidget);
    await tester.tap(find.byType(RaisedButton));
    //how to test navigator?    
  });
}

我有一个正确的方法如何检查，导航器被调用？或者有没有办法模拟和替换导航器？

请注意，上面的代码实际上会因异常而失败，因为在应用程序中没有声明的命名路由 '/nextscreen' . 那个's simple to solve and you don'需要指出来 .

我主要关心的是如何在Flutter中正确地处理这个测试场景 .

3 Answers

以下解决方案是，一般的方法，而不是特定于Flutter .

导航可以从屏幕或小部件中抽象出来 . 测试可以模拟并注入此抽象 . 这种方法应该足以测试这种行为 .

有几种方法可以实现这一目标 . 为了回应这个问题，我将展示其中一个 . 也许有可能简化它或使它更“Darty” .

Abstraction for navigation

class AppNavigatorFactory {
  AppNavigator get(BuildContext context) =>
      AppNavigator._forNavigator(Navigator.of(context));
}

class TestAppNavigatorFactory extends AppNavigatorFactory {
  final AppNavigator mockAppNavigator;

  TestAppNavigatorFactory(this.mockAppNavigator);

  @override
  AppNavigator get(BuildContext context) => mockAppNavigator;
}

class AppNavigator {
  NavigatorState _flutterNavigator;
  AppNavigator._forNavigator(this._flutterNavigator);

  void showNextscreen() {
    _flutterNavigator.pushNamed('/nextscreen');
  }
}

Injection into a widget

class MyScreen extends StatefulWidget {
  final _appNavigatorFactory;
  MyScreen(this._appNavigatorFactory, {Key key}) : super(key: key);

  @override
  _MyScreenState createState() => _MyScreenScreenState(_appNavigatorFactory);
}

class _MyScreenState extends State<MyScreen> {
  final _appNavigatorFactory;

  _MyScreenState(this._appNavigatorFactory);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child: RaisedButton(
                onPressed: () {
                    _appNavigatorFactory.get(context).showNextscreen();
                },
                child: Text(Strings.traktTvUrl)
            )
        )
    );
  }

}

Example of a test （使用Mockito for Dart）

class MockAppNavigator extends Mock implements AppNavigator {}

void main() {
  final appNavigator = MockAppNavigator();

  setUp(() {
    reset(appNavigator);
  });


  testWidgets('Button is present and triggers navigation after tapped',
      (WidgetTester tester) async {

    await tester.pumpWidget(MaterialApp(home: MyScreen(TestAppNavigatorFactory())));

    expect(find.byType(RaisedButton), findsOneWidget);
    await tester.tap(find.byType(RaisedButton));

    verify(appNavigator.showNextscreen());
  });
}

虽然Danny所说的是正确且有效的，但你也可以创建一个模拟的NavigatorObserver来避免任何额外的样板：

class MockNavigatorObserver extends Mock implements NavigatorObserver {}

这将转换为您的测试用例如下：

void main() {
  testWidgets('Button is present and triggers navigation after tapped',
      (WidgetTester tester) async {
    final mockObserver = MockNavigatorObserver();
    await tester.pumpWidget(
      MaterialApp(
        home: MyScreen(),
        navigatorObservers: [mockObserver],
      ),
    );

    expect(find.byType(RaisedButton), findsOneWidget);
    await tester.tap(find.byType(RaisedButton));
    await tester.pumpAndSettle();

    /// Verify that a push event happened
    verify(mockObserver.didPush(typed(any), typed(any)));

    /// You'd also want to be sure that your page is now
    /// present in the screen.
    expect(find.byType(DetailsPage), findsOneWidget);
  });
}

我在我的博客which you can find here上写了一篇深入的文章 .

在navigator tests in the flutter repo中，他们使用NavigatorObserver类来观察导航：

class TestObserver extends NavigatorObserver {
  OnObservation onPushed;
  OnObservation onPopped;
  OnObservation onRemoved;
  OnObservation onReplaced;

  @override
  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onPushed != null) {
      onPushed(route, previousRoute);
    }
  }

  @override
  void didPop(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onPopped != null) {
      onPopped(route, previousRoute);
    }
  }

  @override
  void didRemove(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onRemoved != null)
      onRemoved(route, previousRoute);
  }

  @override
  void didReplace({ Route<dynamic> oldRoute, Route<dynamic> newRoute }) {
    if (onReplaced != null)
      onReplaced(newRoute, oldRoute);
  }
}

这看起来应该做你想要的，但是它可能只能在顶级（MaterialApp）工作，我不确定你是否可以只将它提供给一个小部件 .

如何在Flutter中通过Navigator测试导航

3 Answers

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