等待 Async Void 方法调用进行单元测试

问题描述

我有一个看起来像这样的方法:

I have a method that looks like this:

private async void DoStuff(long idToLookUp)
{
    IOrder order = await orderService.LookUpIdAsync(idToLookUp);

    // Close the search
    IsSearchShowing = false;
}

//Other stuff in case you want to see it
public DelegateCommand<long> DoLookupCommand{ get; set; }
ViewModel()
{
     DoLookupCommand= new DelegateCommand<long>(DoStuff);
}

我正在尝试像这样对其进行单元测试:

I am trying to unit test it like this:

[TestMethod]
public void TestDoStuff()
{
    //+ Arrange
    myViewModel.IsSearchShowing = true;

    // container is my Unity container and it setup in the init method.
    container.Resolve<IOrderService>().Returns(orderService);
    orderService = Substitute.For<IOrderService>();
    orderService.LookUpIdAsync(Arg.Any<long>())
                .Returns(new Task<IOrder>(() => null));

    //+ Act
    myViewModel.DoLookupCommand.Execute(0);

    //+ Assert
    myViewModel.IsSearchShowing.Should().BeFalse();
}

我的断言在我完成模拟的 LookUpIdAsync 之前被调用.在我的正常代码中，这正是我想要的.但是对于我的单元测试，我不想要那样.

My assert is called before I get done with the mocked up LookUpIdAsync. In my normal code, that is just what I want. But for my Unit test I don't want that.

我正在从使用 BackgroundWorker 转换为 Async/Await.使用后台工作程序，这可以正常运行，因为我可以等待 BackgroundWorker 完成.

I am converting to Async/Await from using BackgroundWorker. With background worker this was functioning correctly because I could wait for the BackgroundWorker to finish.

但似乎没有办法等待异步 void 方法...

But there does not seem to be a way to wait for a async void method...

如何对该方法进行单元测试?

推荐答案

我想出了一种方法来进行单元测试:

I figured out a way to do it for unit testing:

[TestMethod]
public void TestDoStuff()
{
    //+ Arrange
    myViewModel.IsSearchShowing = true;

    // container is my Unity container and it setup in the init method.
    container.Resolve<IOrderService>().Returns(orderService);
    orderService = Substitute.For<IOrderService>();

    var lookupTask = Task<IOrder>.Factory.StartNew(() =>
                                  {
                                      return new Order();
                                  });

    orderService.LookUpIdAsync(Arg.Any<long>()).Returns(lookupTask);

    //+ Act
    myViewModel.DoLookupCommand.Execute(0);
    lookupTask.Wait();

    //+ Assert
    myViewModel.IsSearchShowing.Should().BeFalse();
}

这里的关键是，因为我正在进行单元测试，所以我可以替换我想让异步调用(在我的异步无效内)返回的任务.然后，在继续之前，我只需确保任务已完成.

The key here is that because I am unit testing I can substitute in the task I want to have my async call (inside my async void) to return. I then just make sure the task has completed before I move on.

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