Unit Testing Guidelines


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Unit Testing Guidelines

  1. 1. Unit Testing Guidelines Why, What and How...@jhooks | 2010 | joelhooks.com
  2. 2. Why? It’s such a pain. there is never enough time!@jhooks | 2010 | joelhooks.com
  3. 3. Sanity. Developers want a productive environment where things work as expected. Unit test can help create this environment at the code level.@jhooks | 2010 | joelhooks.com
  4. 4. Protect your work. We work hard on the functionality that we add to the application. Unit tests serve as a guard against accidental “harm” of code.@jhooks | 2010 | joelhooks.com
  5. 5. Developer documentation. Well written unit test provide excellent documentation for other developers. Unit tests describe how a piece of logical code should work in a way that English language docs often can’t.@jhooks | 2010 | joelhooks.com
  6. 6. Collective ownership. Code that is protected can be worked on by anybody with greater assurance that nothing will be accidentally broken.@jhooks | 2010 | joelhooks.com
  7. 7. Fearless refactoring. Code can be constantly improved upon with less fear of accidental breakage. Unit tests verify that changes don’t break the existing logic.@jhooks | 2010 | joelhooks.com
  8. 8. What should be tested? Models Service classes Commands Utility classes any other logical code@jhooks | 2010 | joelhooks.com
  9. 9. When to write tests... Before you write the code? After you write the code?@jhooks | 2010 | joelhooks.com
  10. 10. Test Driven Development 10 Ways to Improve Your Code - Neal Ford@jhooks | 2010 | joelhooks.com
  11. 11. Less fear. Writing unit tests firsts lets you focus on the functionality you are adding. Write the test. Write the code. Tests pass. Done.@jhooks | 2010 | joelhooks.com
  12. 12. Ensure test coverage. Tests written before production code ensures that the production code is tested. Tests are not an afterthought.@jhooks | 2010 | joelhooks.com
  13. 13. Reduces tedium of testing. Wait... What?! Writing tests before the production code eliminates the need for a massive testing effort after the code is written.@jhooks | 2010 | joelhooks.com
  14. 14. Guarantees testable code. Testing first ensures that the production code can be tested. Testing after often results in the discovery that the code isn’t testable without refactoring. Refactoring that isn’t protected by tests.@jhooks | 2010 | joelhooks.com
  15. 15. TDD is not a guarantee. Like most practices, TDD is no guarantee of quality or success in development. It is a tool.@jhooks | 2010 | joelhooks.com
  16. 16. So when should I test? Test driven development is not required. Try it out. It can be painful to start, but once you get a rhythm going the benefits are very real.@jhooks | 2010 | joelhooks.com
  17. 17. What is a good unit test? automated repeatable run by anybody future use fast single push easy@jhooks | 2010 | joelhooks.com
  18. 18. Unit tests are by developers for developers. Quality over quantity please.@jhooks | 2010 | joelhooks.com
  19. 19. Trustworthy Developers will run and use tests they trust. A trustworthy test is free of bugs and does what it says it does.@jhooks | 2010 | joelhooks.com
  20. 20. Tests are written to last. Most tests are not meant to be temporary. They change for very specific reasons Bugs in production code Bugs in the test API updates in the production code Test is no longer valid or is not needed To eliminate duplication@jhooks | 2010 | joelhooks.com
  21. 21. There is no logic in the test. Logic in a unit tests makes the test harder to read and understand. There is more likely to be bugs in the test. It can also make the test harder to name. There should be no switch, if, or else statements. There should be no for each, for, or while statements. The test is a series of method calls with no control flow.@jhooks | 2010 | joelhooks.com
  22. 22. Only one thing is tested. A unit test is testing a single behavior. Testing multiple things makes a test hard to understand. Assert only one thing. Should be easy to name (you don’t need an and in the name). When it fails, it is clear what actually failed.@jhooks | 2010 | joelhooks.com
  23. 23. Maintainable Unmaintainable tests are ignored and are often simply removed from the suite. Unmaintainable tests cannot be trusted.@jhooks | 2010 | joelhooks.com
  24. 24. Test the API Unit tests are written against the public contract of the unit being tested. We shouldn’t be trying to test private methods. Private and protected methods can affect the outcome of public methods. Does it make sense to make a private method public? Test the results of the public API that uses private methods Is the private method pure utility? Would it makes sense as a static method of a utility class?@jhooks | 2010 | joelhooks.com
  25. 25. Avoid duplication (DRY) Avoiding the duplication of code in unit tests is as, if not more, important than it is with production code. Create helper methods like factories to assist in setup of common items Use setup methods for setup of items common to all test methods in the case Setup should be as short, simple, and as easy to read as possible@jhooks | 2010 | joelhooks.com
  26. 26. Tests should be isolated. Don’t try to use Parsley, configure and access remote services, or otherwise try to simulate the broader application in a unit test. Are test methods constrained to a linear order of execution? Is the test calling other test methods? Do tests share global state? Test behaviors, not workflows. If shared state can’t be avoid, be sure to reset it in the teardown.@jhooks | 2010 | joelhooks.com
  27. 27. Avoid multiple asserts. Unit tests are testing specific single behaviors. It seems like more work because results might be related, but the results should be verified independently. Give each assertion its own test Give each test a meaningful name This makes failures easy to understand and fix@jhooks | 2010 | joelhooks.com
  28. 28. Avoid over-specification. Tests shouldn’t make assumptions about the implementation of behavior, instead they should focus on the results of the behavior. Does the test specify purely internal behavior of the unit? Is the test using complicated mock objects when simple stubs would be enough? Does the test assume specific results when it isn’t required?@jhooks | 2010 | joelhooks.com
  29. 29. Readable Code in tests is easy to understand quickly. What is being tested is recognizable instantly without deciphering or translation. Readable tests are more trustworthy and maintainable.@jhooks | 2010 | joelhooks.com
  30. 30. Standard test names. If all tests are named in the same pattern they will be easy to read.. methodUnderTest_descriptionOfState_expectedBehavior()@jhooks | 2010 | joelhooks.com
  31. 31. Good variable names. As with all code, good variable names can help greatly in making the code readable. Avoid abbreviations Use static constants instead of hardcoded values@jhooks | 2010 | joelhooks.com
  32. 32. Consistent test structure. Setup -> Action -> Assert [Test] public function doSomeWork_workWasDone_isTrue() { //setup var aDependency:ISomeDependency = new SomeDependency(); //execute behavior aDependency.doSomeWork(); //verify expected state is valid assertThat(allTestsNeedThis.workWasDone, isTrue()); }@jhooks | 2010 | joelhooks.com