检测财产异步方法设置 [英] Testing property set by async method

问题描述

我尝试测试与NUnit的一类，它包含异步方法。我不知道该怎么做以正确的方式。

I try to test a class with NUnit that contains async methods. I don't know how to do it in a correct way.

我有一个类是这样的：

public class EditorViewModel:INotifyPropertyChanged
{
    public void SetIdentifier(string identifier)
    {
         CalcContentAsync();
    }

    private async void CalcContentAsync()
    {
         await SetContentAsync();
         DoSomething();
    } 

    private async Task SetContentAsync()
    {
        Content = await Task.Run<object>(() => CalculateContent());
        RaisePropertyChanged("Content");
    }

    public object Content { get; private set; }

    ...
}

我怎么能写NUnit的测试，即检查，该内容属性设置为正确的价值？我想要做这样的事情：

How can I write a Test in NUnit, that checks, that the Content-Property is set to the right value? I want to do something like that:

[Test]
public void Content_WhenModifierIsXXX_ReturnsSomeViewModel()
{
    var viewModel = new EditorViewModel();

    viewModel.SetIdentifier("XXX");

    Assert.That(viewModel.Content, Is.InstanceOf<ISomeContentViewModel>());
}

但是，这并不工作。由于异步code尚未断言之前执行。

But that doesn't work. Because the asynchronous code has not been executed before the assertion.

推荐答案

您 SetIdentifier 方法异步太（或者你需要使它异步，因为你等着里面的操作然后，你的方法可以看起来像下一个：

Your SetIdentifier method is async too (or you need to make it async because you wait operation inside it. Then your method can looks like next one:

public async Task SetIdentifier(string identifier)
{
     await SetContentAsync();
     DoSomething();
}

而现在你可以等待它在你的单元测试：

And now you can just await it in your unit test:

[Test]
public async Task Content_WhenModifierIsXXX_ReturnsSomeViewModel()
{
    var viewModel = new EditorViewModel();

    await viewModel.SetIdentifier("XXX");

    Assert.That(viewModel.Content, Is.InstanceOf<ISomeContentViewModel>());
}

您也可以使用变通方法来调用您的测试在同步方式：

You can also use workaround to call your test in a sync manner:

[Test]
public async Task Content_WhenModifierIsXXX_ReturnsSomeViewModel()
{
    Task.Run(async () =>
    {
        var viewModel = new EditorViewModel();

        await viewModel.SetIdentifier("XXX");

        Assert.That(viewModel.Content, Is.InstanceOf<ISomeContentViewModel>());
    }).GetAwaiter().GetResult();
}

MSDN杂志。

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