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Rhino Mocks Caveat: Expect.Call / Setup.For / Stubs and Defaults

I got bitten by not knowing some Rhino Mocks API details today. I had some tests written a certain way which were passing and some others written the same way which were failing. (Code can be found here.) In the case of the successful tests, Rhino Mocks appeared to be properly returning a mock object when a property was called on another mock, and in the case of the failing tests it was returning nulls for the property on a mocked object. There didn’t appear to be any difference in the way I needed to declare and setup the mocks used in the test, but there was a subtle one: the code that passed the tests only accessed the property once, whereas the code that failed accessed it multiple times. Because of the way I set up my mocks, a mock was returned for the property the first time it was accessed only.

If you use Expect.Call(…).Return(someObject), by default the method/property will only return the specified object once. If you use a stub or SetupResult.For(…).Return(someObject), by default the method/property will return the specified object as many times as it is called.

Since I prefer the consistency of using Expect.Call for any kind of expectation (and I think it reads better), I used Expect.Call(…).Return(someObject).Repeat.Any() to allow the property to return what I wanted every time it was called.

File this under the importance of defaults.

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