使用Future.delayed时测试中断 [英] Test breaks when using Future.delayed

问题描述

我使用了 Future.delayed 来显示使用以下代码在1秒钟内创建一个FAB：

I have used a Future.delayed to show a FAB in 1 second using this code:

Future.delayed(const Duration(seconds: 1), () {
  setState(() {
    _showFab = true;
  });
});

现在，最基本的烟雾测试已停止工作：

Now the most basic smoke test has stopped working:

void main() {
  testWidgets('smoke test', (WidgetTester tester) async {
    await tester.pumpWidget(MyApp());

    expect(find.byType(MyHomePage), findsOneWidget);
  });
}

这是错误消息：

══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following assertion was thrown running a test:
A Timer is still pending even after the widget tree was disposed.
'package:flutter_test/src/binding.dart': Failed assertion: line 933 pos 7:
'_currentFakeAsync.nonPeriodicTimerCount == 0'    import 'dart:async';

这里是所有使用的代码：

Here is all the code used:

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

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

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

class _MyHomePageState extends State<MyHomePage> {
  bool _showFab = false;

  @override
  Widget build(BuildContext context) {
    Future.delayed(const Duration(seconds: 1), () {
      setState(() {
        _showFab = true;
      });
    });

    return Scaffold(
      floatingActionButton: AnimatedOpacity(
        opacity: _showFab ? 1.0 : 0.0,
        duration: Duration(milliseconds: 1400),
        child: FloatingActionButton(
          onPressed: null,
          child: Icon(Icons.add),
        ),
      ),
    );
  }
}

如何更改单元测试以进行测试通过？

How can I change the unit test to make the test pass?

推荐答案

您需要给测试人员足够的时间来处理您计划的所有异步调用，并尝试更改烟雾测试到这样的东西：

You need to give the tester enough time to process all the async calls you have scheduled, try change your smoke test to something like this:

void main() {
    testWidgets('smoke test', (WidgetTester tester) async {
    await tester.pumpWidget(MyApp());
    // Since you wait 1 second to start the animation and another 1.4 to complete it
    await tester.pump(Duration(seconds: 3));

    expect(find.byType(MyHomePage), findsOneWidget);
  });
}

您还需要移动 Future.delayed 从 build（）方法中删除，因为每次调用 setState（）<时，这都会导致循环行为/ code>再次调用 build（），像这样更改状态：

You will also need to move the Future.delayed out of the build() method, because this is causing a cyclic behaviour, every time you call setState() the build() is called again, change your state like that:

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

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

class _MyHomePageState extends State<MyHomePage> {
  bool _showFab = false;

  @override
  void initState() {
    Future.delayed(const Duration(seconds: 1), () {
      setState(() {
        _showFab = true;
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: AnimatedOpacity(
        opacity: _showFab ? 1.0 : 0.0,
        duration: Duration(milliseconds: 1400),
        child: FloatingActionButton(
          onPressed: null,
          child: Icon(Icons.add),
        ),
      ),
    );
  }
}

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