Moq 使用 ReturnsAsync 并修改 It.IsAny 输入参数

Question

When using ReturnsAsync, we could only get it to return a new object. Is there a better / more correct way to write the code below?

In this example, we have some sort of repository, and our implementation takes in an object of type Thing that has an Id (we want to pretend that our db set the Id) property:

var repo = new Mock<IRepositoryOfThings>();

//Is there a better way to do this perhaps using ReturnsAsync??
repo.Setup(r => r.Add(It.IsAny<Thing>())).Returns(
    (Thing x) =>
    {
        var tcs = new TaskCompletionSource<Thing>();
        x.Id = Guid.NewGuid().ToString();
        tcs.SetResult(x);
        return tcs.Task;
    });

Thanks!

Answer 1

This is the best I could find:

var repo = new Mock<IRepositoryOfThings>();

repo.Setup(r => r.Add(It.IsAny<Thing>())).Returns(
    (Thing x) =>
    {
        x.Id = Guid.NewGuid().ToString();
        return Task.FromResult(x);
    });

It's effectively the same as your answer but only very slightly shorter.

Answer 2

You can just initialize an instance of Thing and return that instance in your setup.

   var repo = new Mock<IRepositoryOfThings>();
   var thing = new Thing
   {
       Id = Guid.NewGuid().ToString()
   };
   repo.Setup(r => r.Add(It.IsAny<Thing>())).ReturnsAsync(thing);