Unit Testing

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Unit Testing presentation going through advantages, naming convention, testing frameworks, mocking frameworks...

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Unit Testing

  1. 1. Unit Testing François Camus
  2. 2. Advantages  Quick feedback loop  Run all tests to know if something is broken  Less need to run application to debug production code  Can debug from test method instead  Provides confidence  Refactoring  Releasing more often  Documents production code behaviour  Serves as production code safety net  Avoids Change And Pray syndrome (CPD)
  3. 3. Test Project  Contains tests for a specific project  Naming convention  To avoid confusion  e.g. when browsing files  e.g. when having lots of tabs  Library namespace  e.g. OpenControl.Web.Mappers  Library Test Project namespace  e.g. OpenControl.Web.Mappers.Tests  Test Class name  e.g. ModelMapperTests  Test project to follow same structure as project being tested
  4. 4. Unit Testing frameworks  Microsoft Test framework   NUnit  xUnit.net  http://xunit.codeplex.com/wikipage?title=Comparisons
  5. 5. Test Execution Lifecycle  Initialization (before each test execution)  initialises dependencies and fields that are common to many tests  no setup here: each test does its own setup  Easier to maintain test code  Don’t want spaghetti test code all depending on a common setup method  Execution  Does local test setup  Calls method to test passing parameters and storing result if any  Asserts something on result or behaviour  Cleanup (after each test execution)  Dispose of initialized dependencies  Test Class initialisation and cleanup  Usually used by custom testing framework  e.g. Tester base class containing test helpers  Initialises before first test execution  Cleans up after last test execution
  6. 6. Test method naming convention [Fact] public void Method_Condition_Result() {} 1. Method being tested 2. Condition to meet test result (optional) 3. Test result [Fact] public void GetData_DataExists_ReturnsData() {}
  7. 7. Test method structure  AAA: Arrange/Act/Assert 1. Arrange: local test setup 2. Act: calls method to test 3. Assert: asserts result or behaviour  Common structure to all tests  Easier for other developers to maintain code  Helpful when doing Test Driven Development
  8. 8. Interaction based Unit Testing  Asserting expectation on method  Couples to internal implementation  Less flexible to do refactoring  Leads to fragile tests  Easier when starting unit testing  Unavoidable  Need them when unable to only test result  e.g Testing that a void method was called  About 10% of tests  http://programmaticallyspeaking.com/?p=713
  9. 9. State based Unit Testing  Tests method result rather than expectation  Easier to maintain  Only local test setup may need amendment  Preferred form of unit testing
  10. 10. Testing internals  Add attribute to production code assembly info to make internals visible to specific library [assembly: InternalsVisibleTo("OpenControl.ClassLibrary.Tests")]  http://ayende.com/Wiki/Rhino+Mocks+- +Internal+Methods.ashx
  11. 11. One assert per test  Atomic  Easier to understand  Easier to maintain  When refactoring production code, you get better feedback on what breaks
  12. 12. Dependency Injection  Constructor parameter injection  Property injection
  13. 13. Mocking  Mocking frameworks (all based on Castle Dynamic Proxy)  http://www.castleproject.org/projects/dynamicproxy/  Add attribute to production code assembly info: [assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]  NSubstitute  Shorter but awkward syntax  Less lambda so changing developers’ habits  Rhino Mocks  Too big (“Does the coffee !” Manu)  Confusion for new users on which syntax to use  Latest syntax is following state based unit testing approach  But old syntax remains  Large community  Moq  Smaller and simpler  Large community  http://code.google.com/p/moq/wiki/QuickStart
  14. 14. Tools  Test Driven .Net (visual studio extension)  Works with xUnit.net (may need to run xunit installer to add support to Test Driven .Net)  ReSharper...  Jenkins  After build runs tests via plugin (xUnit plugin...)  Need to upgrade Jenkins to support .NET 4+
  15. 15. Conclusion  Questions ?  TDD next time

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