有没有一种方法进行单元测试异步方法？ [英] Is there a way to unit test an async method?

问题描述

我使用的xUnit和NMock在.NET平台。 我测试presentation模型，其中一个方法是异步的。 该方法创建一个异步任务，并执行它因此该方法立即返回，而我需要检查的状态都还没有准备好。

I am using Xunit and NMock on .NET platform. I am testing a presentation model where a method is asynchronous. The method creates an async task and executes it so the method returns immediately and the state I need to check aren't ready yet.

我可以设置完成后，一个标志，而无需修改SUT，但是这将意味着我将不得不继续检查的标志，例如一个while循环，有可能超时。

I can set a flag upon finish without modifying the SUT but that would mean I would have to keep checking the flag in a while loop for example, with perhaps timeout.

我有什么选择？

推荐答案

请问你的对象的功能，异步方法完成，如事件任何类型的信号？如果是这样的话，你可以用下面的办法：

Does your object feature any sort of signal that the asynchronous method is finished, such as an event? If that is the case, you can use the following approach:

[Test]
public void CanTestAsync()
{
    MyObject instance = new MyObject()
    AutoResetEvent waitHandle = new AutoResetEvent(false); 
    // create and attach event handler for the "Finished" event
    EventHandler eventHandler = delegate(object sender, EventArgs e) 
    {
        waitHandle.Set();  // signal that the finished event was raised
    } 
    instance.AsyncMethodFinished += eventHandler;

    // call the async method
    instance.CallAsyncMethod();

    // Wait until the event handler is invoked
    if (!waitHandle.WaitOne(5000, false))  
    {  
        Assert.Fail("Test timed out.");  
    }  
    instance.AsyncMethodFinished -= eventHandler;    
    Assert.AreEqual("expected", instance.ValueToCheck);
}

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