Ouch, pained my brain over this one for the last half hour or so, but finally found the solution. I had a call similar to: repository .Stub(x => x.TryGet(<Specification>.Matches(y => y.Something), Arg<Customer>.Out(customerToReturn).Dummy)) .Return(true); Because my first argument had a fairly large Matches call (it’s simplified here), I refactored it to: var specification = Arg<Specification>.Matches(y => y.Something); repository .Stub(x => x.TryGet(specification, out Arg<Customer>.Out(customerToReturn).Dummy)) .Return(true); Ah, much more readable! Only, it didn’t work. The exception I got was: Use Arg<T> ONLY within
Someone once said something like: “Code is written once and read many times”. That is why I propose not to use RhinoMocks’ AssertWasCalled method for methods that accept parameters. Sure, it’s written faster than using GetArgumentsForCallsMadeOn, but check out the error message you get for this: var expectedMessage = “RhinoMocks baby!”; var actualMessage = “RhinoMocks dude!”; var fooMock = MockRepository.GenerateMock(); fooMock.Bar(actualMessage); fooMock.AssertWasCalled(x => x.Bar(expectedMessage)); Your test will fail with the following message: IFoo.Bar(“RhinoMocks baby!”); Expected #1, Actual #0. To fix