如何在Flutter中通过Navigator测试导航

Question

比方说,我在Flutter中使用了一个屏幕测试WidgetTester.有一个按钮,通过执行导航Navigator.我想测试该按钮的行为.

空间/屏幕

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)
            )
        )
    );
  }

}

测试

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'/nextscreen'在应用程序中没有声明命名的路由.这很容易解决,你不需要指出它.

我主要关心的是如何在Flutter中正确地处理这个测试场景.

Answer 1

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);
  });
}

我在博客上写了一篇关于这个的深入文章,你可以在这里找到.

Answer 2

在flutter仓库中的导航器测试中，他们使用NavigatorObserver类观察导航：

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);
  }
}

看起来它应该可以满足您的要求，但是它只能在顶层（MaterialApp）上运行，我不确定是否可以仅将其提供给小部件。