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Mocking 101


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Slides from the wellington Dot net user group mocking talk on 2nd April 2008

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Mocking 101

  1. 1. A brief introduction to test doubles and mocking frameworks
  2. 2. Unit testing goals <ul><li>Verification </li></ul><ul><li>Feedback Speed </li></ul><ul><li>Focus </li></ul><ul><li>Isolation </li></ul>
  3. 3. Test Doubles <ul><li>4 types of test double </li></ul><ul><ul><li>Dummy – We just pass it round and don’t do anything with it </li></ul></ul><ul><ul><li>Fake – Working implementations but take shortcuts </li></ul></ul><ul><ul><li>Stubs – Canned answers to expected calls </li></ul></ul><ul><ul><li>Mocks – Pre programmed with responses and expectations that certain calls should be made </li></ul></ul>
  4. 4. Why? <ul><li>Feedback cycle needs to be as small as possible to be useful </li></ul><ul><li>We need to remove pain points from being necessary </li></ul><ul><ul><li>Database calls </li></ul></ul><ul><ul><li>UI </li></ul></ul><ul><ul><li>Third party libraries </li></ul></ul><ul><li>We can remove reliance on the rest of the code being complete before knowing the current unit works </li></ul>
  5. 5. Mocking frameworks <ul><li>Provide a repeatable way to set up mocks/stubs/fakes with little code cost. </li></ul><ul><li>Test logic can stay within test </li></ul><ul><li>We can develop as we test and get immediate results (TDD) </li></ul>
  6. 6. Rhino.Mocks <ul><li>One of the most mature and feature complete mocking frameworks </li></ul><ul><li>Uses castle remoting to mock calls </li></ul><ul><ul><li>Not able to mock static or sealed calls </li></ul></ul><ul><li>Fast </li></ul><ul><li>Record/Replay Syntax </li></ul><ul><li>Lots of help and code examples available </li></ul><ul><li>Open Source </li></ul>
  7. 7. Typemock Isolator <ul><li>Mature and fully featured </li></ul><ul><li>Uses IL Generation </li></ul><ul><ul><li>Can mock static classes and calls </li></ul></ul><ul><ul><li>Can chain events </li></ul></ul><ul><li>Commercial licence available for full feature set and support </li></ul><ul><li>Main commercial mocking framework so features ++ </li></ul>
  8. 8. Moq <ul><li>New Kid on the block </li></ul><ul><li>.net 3.5 only </li></ul><ul><li>No record/replay semantics, just expectations </li></ul><ul><li>Less code clutter to tests </li></ul><ul><li>Not feature complete </li></ul><ul><li>In active development </li></ul><ul><li>Open source </li></ul>
  9. 9. How? <ul><li>It’s time to code </li></ul>
  10. 10. Links <ul><li>Rhino Mocks: </li></ul><ul><li>Typemock: </li></ul><ul><li>Moq: </li></ul><ul><li>Me: [email_address] </li></ul>