Returning value that was passed into a method

Question

I have a method on an interface:

string DoSomething(string whatever);

I want to mock this with MOQ, so that it returns whatever was passed

Answer 1

Even more useful, if you have multiple parameters you can access any/all of them with:

_mock.Setup(x => x.DoSomething(It.IsAny(),It.IsAny(),It.IsAny())
     .Returns((string a, string b, string c) => string.Concat(a,b,c));

You always need to reference all the arguments, to match the method's signature, even if you're only going to use one of them.