代码之家 › 专栏 › 技术社区 › Mary

如何测试initState()中存在异步调用的颤振应用程序?

flutter dart testing asynchronous

Mary · 技术社区 · 7 年前

我有一个StatefulWidget,在它的 initState() ,以构建小部件。当我手动运行这个程序时,小部件确实构建得很快。

然而,在我的测试中,即使我使用 await tester.pump() 或 await tester.pumpAndSettle() ,小部件似乎不会构建,直到测试运行之后。

Widget _coolWidget;

@override
void initState() {
  super.initState();
  _coolWidget = Container(); // If I set this to OverflowBox() my test passes
  _buildWidgetFromCanvas();
}

Future<void> _buildWidgetFromCanvas() {
  final ui.PictureRecorder recorder = ui.PictureRecorder();
  final ui.Canvas canvas = ui.Canvas(recorder);
  // ... more canvas drawing code ...
  final img = ... // Image.memory() I build from the canvas
  if (!mounted) {
    print('no longer mounted');
    return;
  }

  setState(() {
    print(img);
    _coolWidget = OverflowBox(
      child: img,
    );
    print(_coolWidget);
  });
}

测试代码:

void main() {
  testWidgets('''OverflowBox shows up.''', (WidgetTester tester) async {
    await _setUp(tester); // Just instantiates my widget in an app
    await tester.pumpAndSettle();
    expect(find.byType(OverflowBox).evaluate().length, 1);
  });
}

在中运行测试结果时的输出:

failed: Error caught by Flutter test framework, thrown running a test.
Expected: <1>
Actual: <0>

但如果我设定 _coolWidget = OverflowBox(); 在里面 initState() ,测试通过。

print(img); 和 print(_coolWidget); 并正确记录绘制的图像。

我也得到了 no longer mounted 打印,但这只发生在最后一次打印时,在Flitter内置之前 (tearDownAll)

在pump()和pumpAndSettle()中设置持续时间似乎不会改变任何事情。

1 回复 | 直到 7 年前

Dan Field 7 年前

考虑使用 FutureBuilder build 方法依赖于异步工作。


Future<Image> _buildWidgetFromCanvas() {
  final ui.PictureRecorder recorder = ui.PictureRecorder();
  final ui.Canvas canvas = ui.Canvas(recorder);
  // ... more canvas drawing code ...
  if (!mounted) {
    return null
  }
  final img = ... // Image.memory() I build from the canvas
  return img;
}

FutureBuilder<Image>(
  future: _buildWidgetFromCanvas, // a previously-obtained Future<Image> or null
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    switch (snapshot.connectionState) {
      case ConnectionState.none:
      case ConnectionState.active:
      case ConnectionState.waiting:
        return SizedBox(height: <height>, width: <width>);
      case ConnectionState.done:
        return OverflowBox(child: snapshot.data);
    }
    return null; // unreachable
  },
)

  expect(find.byType(OverflowBox), findsOneWidget);

Alex Rindone 6 年前

我有一个未来的建设者在等待,它没有完成或抛出任何错误。futurebuilder有一个加载文件的未来,因此它应该能够这样做。应用程序工作正常,但测试不正常。

    // Create the widget by telling the tester to build it.
    await tester.pumpWidget(
        MaterialApp(home: DisplayPictureScreen(key: _globalKey, imagePath: 'test.png', onUpload: upload))
    );
    // Create the Finders.
    final safeAreaFinder = find.byKey(_globalKey);
    // expect we have one positioned widget
    expect(safeAreaFinder, findsOneWidget);
    await tester.pump();
    expect(find.byType(CircularProgressIndicator), findsOneWidget);
    // test code here
    await tester.pump(const Duration(seconds: 20));
    expect(find.byType(Expanded), findsOneWidget);
  });
}```