RhinoMock vs. TypeMock vs. NUnit's Mocking?

Question

I am just starting to do Test Driven Development, and I am wondering the major differences between RhinoMock, TypeMock, and NUnit's built-in mocking?

Any information would be greatly appreciated!

Answer 1

TypeMock is a commercial product (meaning you'll have to pay for it) but will allow you to mock concrete objects - unlike RhinoMocks/NUnit/MoQ which can only mock an interface/abstract class. How it achieves this is borderline black magic, but it does some very clever things with the CLR.

This can be particularly useful when you use libraries in your project that don't use many interfaces. So you could, for example, use TypeMock to mock out a LINQtoSQL datacontext, or Sharepoint objects. However, if you are using TypeMock this is no excuse for bad design in your application.

As far as I'm aware, aside from minor syntax differences, most of the mocking frameworks have moved away from the old record/playback model. Commonly, you set up your mocks by writing expectations using a Fluent Interface.

Personally, I have only used MoQ and I <3 it.

Answer 2

A video called TDD - Understanding Mock Objects by Roy Osherove is very helpful in learning the differences of the different mocking libraries. He doesn't go in great detail of every aspect, but enough for you to understand. I hope this helps. Roy is also the Chief Architect for TypeMock and is a very influential figure in the unit testing arena. I couldn't recommend this video enough for someone who wants to learn how to use mocking and also learn about the library's available.

The main difference between TypeMock and the open-source library's is that TypeMock uses the Profiler API provided by Microsoft instead of a dynamic proxy. This allows TypeMock to mock concrete classes and static methods. In case you aren't sure what the profiler is, it is the same API that is used by tools like JetBrain's dotTrace and RedGate's Ants .Net profilers. TypeMock just uses the API in a different way to fake(mock) what you tell it to.

@RichardOD, thanks for the reminder, his book "The Art of Unit Testing" goes into greater detail where the video doesn't. I own the book and it is very informative.

Answer 3

• Rhino.Mocks is an open source, continuously developed and improving framework by one of the industry's most prolific developers. It has been around for a while and hence supports quite a few different paradigms for mocking. It can be a little tougher to learn therefore in the sense that you might find tutorials for the "old" way of doing things. Here's a tip, SetUpResultFor() and Expect.Call() are the old ways of doing things. The new way is mockObject.AssertWasCalled().

I have not had any personal experience with these others but...

• MOQ is an open source, continuously developed and improving framework by one of the industry's somewhat less prolific developers (as compared to Ayende). It is newer and therefore lacks some features that Rhino.Mocks has. This is usually not a problem since these features tend to be ones that are somewhat deprecated in Rhino. I have heard that because of this it is slightly easier to learn (mocking frameworks aren't hard to learn by the way).
• NUnit Mocks is very quaint as far as mocking goes. It doesn't support the currently preferred Arrange-Act-Assert syntax relying instead on Expect-Verify (record/replay). It also relies on strings to identify method and property names instead of lambdas. This makes it significantly resistant to refactoring. This is a serious problem. I would not recommend it.
• TypeMock Isolater is a hardcore for-pay mocking framework from a company (owned by?) Roy Osherove - a guy who knows his testing but also has some mildly controversial opinions as to how to apply it. It is really intense as far as what it can do - getting down to the low level and modifying how CLR objects work. The philosophy behind TypeMock isn't really 100% TDD however. Part of the benefits of TDD is that by embracing the limitations of Mocking frameworks you will design better code. TypeMock blasts those limitations to pieces. As far as I know it is mostly used by people who are trying to get code they have no control over under test.

Answer 4

I use TypeMock all the time and have found it to be a very powerful tool that can improve the coverage of my unit tests. This is because I work with SharePoint and only TypeMock can allow me to mock out SharePoint classes - since they are concrete classes and not interfaces.

Mocking SharePoint classes is not possible with RhinoMock, Moq, NUNit, etc since (I believe) they require interfaces to mock objects, rather then being able to mock the actual concrete classes.

If your code does use a lot of interfaces, and you don't require mocking concrete classes then TypeMock is a bit pricey, but for the power you get, it's worth it.