如何单元测试Flutter TextFormField maxlines

Question

是否可以编写一个单元测试来验证TextFormField的maxLines属性是否设置正确。我找不到访问该属性的方法：

我创建一个TextFormField

final field = TextFormField(
    initialValue: "hello",
    key: Key('textformfield'),
    maxLines: 2,
  );

然后在测试中我可以使用tester.widget访问表单字段

 final formfield =
    await tester.widget<TextFormField>(find.byKey(Key('textformfield')));

但是由于maxLines属性被传递给返回Textfield的Builder，我如何才能访问textfield。

或者还有其他方法可以验证这一点吗？

Answer 1

我不知道这是否是一个很好的解决方案，但是当我设置TextFormField的值时，我可以直接找到EditableText小部件。我可以找到测试属性maxLines的这个小部件。

final EditableText formfield =
    await tester.widget<EditableText>(find.text('testvalue'));

expect(formfield.maxLines, 2);

Answer 2

您可以使用Integration测试对其进行测试。逻辑是在TextFormField中键入更多文本，使其符合预期的文本。 所以我们可以验证TextFormField只允许2个字符，如下所示。 例如零件：

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:font_awesome_flutter/font_awesome_flutter.dart';


void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: SingleChildScrollView(
          child: MyLoginPage(title: 'Flutter Demo Home Page'),
        ),
      ),
    );
  }
}

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

  final String title;

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

class _MyLoginPageState extends State<MyLoginPage> {
  String _email;
  String _password;
  TextStyle style = TextStyle(fontSize: 25.0);

  @override
  Widget build(BuildContext context) {
    final emailField = TextField(
      key: Key('textformfield'),
      obscureText: false,
      maxLength: 2,
      style: style,
      decoration: InputDecoration(
          contentPadding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
          prefixIcon: Icon(FontAwesomeIcons.solidEnvelope),
          hintText: "Email",
          focusedBorder: OutlineInputBorder(
              borderSide: BorderSide(color: Colors.red[300], width: 32.0),
              borderRadius: BorderRadius.circular(97.0))),
      onChanged: (value) {
        setState(() {
          _email = value;
        });
      },
    );
    final passwordField = TextField(
      obscureText: true,
      style: style,
      decoration: InputDecoration(
          contentPadding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
          prefixIcon: Icon(FontAwesomeIcons.key),
          hintText: "Password",
          focusedBorder: OutlineInputBorder(
              borderSide: BorderSide(color: Colors.red[300], width: 32.0),
              borderRadius: BorderRadius.circular(25.0))),
      onChanged: (value) {
        setState(() {
          _password = value;
        });
      },
    );

    return Center(
      child: Column(
        children: <Widget>[
          Container(
            color: Colors.yellow[300],
            height: 300.0,
          ),
          emailField,
          passwordField,
        ],
      ),
    );
  }
}

考试：

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

import 'package:flutter_textfields_up/main.dart';

void main() {
  testWidgets('Email should be only 2 characters', (WidgetTester tester) async {
    // Build our app and trigger a frame.
    await tester.pumpWidget(MyApp());
    var txtForm = find.byKey(Key('textformfield'));
    await tester.enterText(txtForm, '123');

    expect(find.text('123'), findsNothing); // 3 characters shouldn't be allowed
    expect(find.text('12'), findsOneWidget); // 2 character are valid.

  });
}

请注意我发送的是3个字符，TextFormField应该只允许2个字符。 希望这有帮助。