在进行单元测试时，如何模拟异步方法的返回null? [英] When unit testing, how do I mock a return null from async method?

问题描述

通常，我会像这样模拟我的仓库:

Normally, I mock my repo like so:

var repository = new Mock<ISRepository>();
repository.Setup(r => r.GetMemberAsync(email))
    .Returns(Task.FromResult(new Member
    {
        FirstName = firstName,
        LastName = lastName
    }));

但是，在我的代码中，我检查是否未找到该成员，即GetMemberAsync返回null.我该如何嘲笑?

But, in my code, I check to see if the member is not found, i.e. GetMemberAsync returns null. How do I mock this?

我尝试过:

var repository = new Mock<ISRepository>();
repository.Setup(r => r.GetMemberAsync(email))
    .Returns(Task.FromResult<object>(null));

但是出现编译错误.

推荐答案

由于返回的任务与异步方法返回的类型不匹配，因此会出现编译器错误.您应该返回 Task< Member> 而不是简单地 Task< object> :

You get a compiler error because you return a task that doesn't match the type the async method returns. You should return Task<Member> instead of simply Task<object>:

repository.Setup(r => r.GetMemberAsync(email)).Returns(Task.FromResult<Member>(null));

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