Widget测试失败，找不到No MediaQuery小部件

Question

我的问题是关于颤动小部件测试，什么是测试现有小部件包裹新Scaffold（...）的正确方法？我找到MediaQuery.of但它接受BuildContext而不是Widget。

详细信息：我编写了简单的登录表单小部件并尝试为其实现小部件测试。执行测试后，我得到了异常：

Expected: 'Sorry, only customer can login from mobile device. [Mock]'
  Actual: FlutterError:<No MediaQuery widget found.
          Scaffold widgets require a MediaQuery widget ancestor.
          The specific widget that could not find a MediaQuery ancestor was:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee]
          The ownership chain for the affected widget is:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee] ← LoginForm ← [root]
          Typically, the MediaQuery widget is introduced by the MaterialApp or WidgetsApp widget at
          the top of your application widget tree.>
   Which: FlutterError:<No MediaQuery widget found.
          Scaffold widgets require a MediaQuery widget ancestor.
          The specific widget that could not find a MediaQuery ancestor was:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee]
          The ownership chain for the affected widget is:
            Scaffold-[LabeledGlobalKey<ScaffoldState>#8ffee] ← LoginForm ← [root]
          Typically, the MediaQuery widget is introduced by the MaterialApp or WidgetsApp widget at
          the top of your application widget tree.>is not a string

When the exception was thrown, this was the stack:
#4      main.<anonymous closure> (C:\Work\app_mobile\test\login_widget_test.dart:21:5)
<asynchronous suspension>
#5      testWidgets.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:flutter_test\src\widget_tester.dart:61:25)
#6      TestWidgetsFlutterBinding._runTestBody (package:flutter_test\src\binding.dart:471:19)
<asynchronous suspension>
#9      TestWidgetsFlutterBinding._runTest (package:flutter_test\src\binding.dart:458:14)
#10     AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test\src\binding.dart:640:24)
#11     _FakeAsync.run.<anonymous closure> (package:quiver\testing\src\async\fake_async.dart:186:24)
#15     _FakeAsync.run (package:quiver\testing\src\async\fake_async.dart:185:11)
#16     AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test\src\binding.dart:638:16)
#17     testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test\src\widget_tester.dart:60:24)
#18     Declarer.test.<anonymous closure>.<anonymous closure> (package:test\src\backend\declarer.dart:160:19)
<asynchronous suspension>
#19     Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test\src\backend\invoker.dart:206:15)
<asynchronous suspension>
#23     Invoker.waitForOutstandingCallbacks (package:test\src\backend\invoker.dart:203:5)
#24     Declarer.test.<anonymous closure> (package:test\src\backend\declarer.dart:158:29)
<asynchronous suspension>
#25     Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test\src\backend\invoker.dart:351:23)
<asynchronous suspension>
#27     StackZoneSpecification._run (package:stack_trace\src\stack_zone_specification.dart:209:15)
#28     StackZoneSpecification._registerCallback.<anonymous closure> (package:stack_trace\src\stack_zone_specification.dart:119:48)
#33     StackZoneSpecification._run (package:stack_trace\src\stack_zone_specification.dart:209:15)
#34     StackZoneSpecification._registerCallback.<anonymous closure> (package:stack_trace\src\stack_zone_specification.dart:119:48)
#39     _Timer._runTimers (dart:isolate-patch/dart:isolate/timer_impl.dart:367)
#40     _Timer._handleMessage (dart:isolate-patch/dart:isolate/timer_impl.dart:401)
#41     _RawReceivePortImpl._handleMessage (dart:isolate-patch/dart:isolate/isolate_patch.dart:163)
(elided 17 frames from package dart:async and package dart:async-patch)

这是登录表单小部件：

import 'dart:async';
import 'dart:convert';

import 'package:app_facade/app_facade.dart';
import 'package:app_mobile/utils/dependency_injection.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:flutter/services.dart';

class LoginForm extends StatefulWidget {
  const LoginForm({ Key key }) : super(key: key);

  static GlobalKey<FormFieldState<String>> emailFieldKey = new GlobalKey<FormFieldState<String>>();
  static GlobalKey<FormFieldState<String>> passwordFieldKey = new GlobalKey<FormFieldState<String>>();
  static const String routeName = '/';

  @override
  LoginFormState createState() => new LoginFormState();
}

class LoginData {
  String email = '';
  String password = '';
}

class LoginFormState extends State<LoginForm> {
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  LoginData loginData = new LoginData();

  UserApi _userApi;

  void showInSnackBar(String value) {
    _scaffoldKey.currentState.showSnackBar(new SnackBar(
        content: new Text(value)
    ));
  }

  bool _autovalidate = false;
  bool _formWasEdited = false;
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();


  @override
  void initState() {
    super.initState();
    _userApi = new Injector().userApi;
  }

  Future<Null> _handleSubmitted() async {
    final FormState form = _formKey.currentState;
    if (!form.validate()) {
      _autovalidate = true;  // Start validating on every change.
      showInSnackBar('Please fix the errors in red before submitting.');
    } else {
      form.save();
      login();
    }
  }

  Future<Null> login() async {
    try {
      await _userApi.login(loginData.email, loginData.password);
      Navigator.popAndPushNamed(context, '/user');
    } catch (e) {
      showInSnackBar(e.toString());
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _scaffoldKey,
      appBar: new AppBar(
        title: const Text('Some'),
      ),
      body: new Form(
          key: _formKey,
          autovalidate: _autovalidate,
          child: new ListView(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            children: <Widget>[
              new TextFormField(
                key: new Key('email'),
                decoration: const InputDecoration(
                  icon: const Icon(Icons.person),
                  hintText: 'Your email',
                  labelText: 'Email *',
                ),
                onSaved: (String value) { loginData.email = value; },
              ),
              new TextFormField(
                key: LoginForm.passwordFieldKey,
                decoration: const InputDecoration(
                  icon: const Icon(Icons.security),
                  hintText: 'Your password',
                  labelText: 'Password *',
                  ),
                obscureText: true,
                onSaved: (String value) { loginData.password = value; },
              ),
              new Container(
                padding: const EdgeInsets.all(20.0),
                alignment: const FractionalOffset(0.5, 0.5),
                child: new RaisedButton(
                  child: const Text('SUBMIT'),
                  onPressed: _handleSubmitted,
                ),
              ),
              new Container(
                padding: const EdgeInsets.only(top: 20.0),
                child: new Text('* indicates required field', style: Theme.of(context).textTheme.caption),
              ),
            ],
          )
      ),
    );
  }
}

这是小部件测试：

import 'package:app_facade/app_facade.dart';
import 'package:app_mobile/login_form.dart';
import 'package:app_mobile/utils/dependency_injection.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('login widget test', (WidgetTester tester) async {
    Injector.configure(BackendType.MOCK);
    // Tells the tester to build a UI based on the widget tree passed to it
    var loginForm = new LoginForm();
    await tester.pumpWidget(
      loginForm
    );

    tester.enterText(find.byKey(LoginForm.emailFieldKey), "login");
    tester.enterText(find.byKey(LoginForm.passwordFieldKey), "password");

    var exception = tester.takeException();
    print(exception);
    expect(exception, equals('Sorry, only customer can login from mobile device. [Mock]'));
  });
}

我找到MediaQuery.of但不明白它如何与现有的小部件一起使用？它接受BuildContext作为参数。

Answer 1

您需要使用MediaQuery(...)实例包装小部件，并且因为您使用的是Scaffold(..)，所以必须将其包装在MaterialApp(..)

中

Read more about MediaQuery

示例：

Widget testWidget = new MediaQuery(
      data: new MediaQueryData(),
      child: new MaterialApp(home: new LoginForm())
)

Answer 2

**scaffold() 小部件如何成为 MaterialApp() 的子组件的完美示例 **

          import 'package:flutter/material.dart';
   
         class MyApp extends StatelessWidget {

             @override
          Widget build(BuildContext context) {
        return MaterialApp(
         debugShowCheckedModeBanner: false,
           theme: ThemeData(
      primarySwatch: Colors.blue,
      ),
     home: MyHomePage(title: 'title'),
    );
  }
}

        class MyHomePage extends StatefulWidget {
        MyHomePage({Key Key, this.title}) : super(key: Key);

       @override
        _MyHomePageState createState() => _MyHomePageState();

    }

        class _MyHomePageState extends State<MyHomePage> {
    Widget build(BuildContext context) {
      return new Scaffold(
     appBar: AppBar(
    backgroundColor: Colors.transparent,
    title: widget.title
 )

}

Answer 3

我遇到了同样的问题，我也不得不将其包装在MaterialApp中，但是我以其他方式做到了这一点，而没有使用MediaQuery。就我而言，它有效

void main() {

Widget createWidgetForTesting({Widget child}){
return MaterialApp(
  home: child,
);
}

testWidgets('Login Page smoke test', (WidgetTester tester) async {

await tester.pumpWidget(createWidgetForTesting(child: new LoginPage()));

await tester.pumpAndSettle();

});
}