RhinoMocks – Stub a Method That Returns a Parameter

You can provide an implementation for a method with the Do() handler:

Func<TypeX,TypeY,TypeZ,TypeZ> returnThird = (x,y,z) => z;
mock.Expect(x => x.Method(null, null, null)).IgnoreArguments().Do(returnThird);

Note that TypeZ appears twice because it is both an input argument type and the return type.