如何告诉 Moq 返回任务? [英] How can I tell Moq to return a Task?

问题描述

我有一个接口声明

Task DoSomethingAsync();

我使用 MoqFramework 进行测试:

I'm using MoqFramework for my tests:

[TestMethod()]
public async Task MyAsyncTest()
{
   Mock<ISomeInterface> mock = new Mock<ISomeInterface>();
   mock.Setup(arg => arg.DoSomethingAsync()).Callback(() => { <my code here> });
   ...
}

然后在我的测试中，我执行调用 await DoSomethingAsync() 的代码.并且测试只是在那条线上失败了.我做错了什么?

Then in my test I execute the code which invokes await DoSomethingAsync(). And the test just fails on that line. What am I doing wrong?

推荐答案

您的方法没有任何回调，因此没有理由使用 .CallBack().您可以使用 .Returns() 和 Task.FromResult，例如:

Your method doesn't have any callbacks so there is no reason to use .CallBack(). You can simply return a Task with the desired values using .Returns() and Task.FromResult, e.g.:

MyType someValue=...;
mock.Setup(arg=>arg.DoSomethingAsync())        
    .Returns(Task.FromResult(someValue));

更新 2014-06-22

Moq 4.2 有两个新的扩展方法来帮助解决这个问题.

Moq 4.2 has two new extension methods to assist with this.

mock.Setup(arg=>arg.DoSomethingAsync())
    .ReturnsAsync(someValue);

mock.Setup(arg=>arg.DoSomethingAsync())        
    .ThrowsAsync(new InvalidOperationException());

更新 2016-05-05

正如 Seth Flowers 在其他答案中提到的那样，ReturnsAsync 仅适用于返回一个 Task.对于只返回一个 Task 的方法，

As Seth Flowers mentions in the other answer, ReturnsAsync is only available for methods that return a Task<T>. For methods that return only a Task,

.Returns(Task.FromResult(default(object)))

可以使用.

如这个答案所示，在.NET 4.6中，这被简化为.Returns(Task.CompletedTask);，例如:

As shown in this answer, in .NET 4.6 this is simplified to .Returns(Task.CompletedTask);, e.g.:

mock.Setup(arg=>arg.DoSomethingAsync())        
    .Returns(Task.CompletedTask);

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