This document provides an introduction to test doubles and mocking frameworks. It discusses the goals of unit testing, the four types of test doubles (dummy, fake, stub, and mock), and why mocking frameworks are useful. It then summarizes three popular mocking frameworks - Rhino.Mocks, Typemock Isolator, and Moq - noting their key features, strengths, and limitations. The document encourages the reader to start using these frameworks in their own unit testing.

1. A brief introduction to test doubles and mocking frameworks

2. Unit testing goals Verification Feedback Speed Focus Isolation

3. Test Doubles 4 types of test double Dummy – We just pass it round and don’t do anything with it Fake – Working implementations but take shortcuts Stubs – Canned answers to expected calls Mocks – Pre programmed with responses and expectations that certain calls should be made

4. Why? Feedback cycle needs to be as small as possible to be useful We need to remove pain points from being necessary Database calls UI Third party libraries We can remove reliance on the rest of the code being complete before knowing the current unit works

5. Mocking frameworks Provide a repeatable way to set up mocks/stubs/fakes with little code cost. Test logic can stay within test We can develop as we test and get immediate results (TDD)

6. Rhino.Mocks One of the most mature and feature complete mocking frameworks Uses castle remoting to mock calls Not able to mock static or sealed calls Fast Record/Replay Syntax Lots of help and code examples available Open Source

7. Typemock Isolator Mature and fully featured Uses IL Generation Can mock static classes and calls Can chain events Commercial licence available for full feature set and support Main commercial mocking framework so features ++

8. Moq New Kid on the block .net 3.5 only No record/replay semantics, just expectations Less code clutter to tests Not feature complete In active development Open source

9. How? It’s time to code

10. Links Rhino Mocks: http://www.ayende.com/projects/rhino-mocks.aspx Typemock: http://www.typemock.com/ Moq: http://code.google.com/p/moq Me: http://www.bgeek.net [email_address] http://www.twitter.com/buildmaster