How to Love Unit Testing

Unit Testing in Pester
PowerShell Summit 2018

Transcript

1. How to Love Unit Testing Brian Bunke @brianbunke
2. Pester “Pester is the ubiquitous test and mock framework for PowerShell.” https://github.com/pester/Pester @brianbunke
3. Common Questions Am I doing this right? What does a good test even look like? What’s not enough, or too much? @brianbunke
4. Today’s Goals 1. Feel comfortable reading and writing unit tests 2. Know some future pitfalls to watch out for @brianbunke
5. Why Love Test Suites? •Fully automated •Self-documenting •Allows support to scale •Improves code reviews @brianbunke
6. Integration Tests @brianbunke
7. Integration Testing Pain Points • Require infrastructure • Slow • Service interruptions • Order of tests matters • Root cause isolation @brianbunke
8. Falling in Love
9. What is Unit Testing? 1. Making your test suite discrete 2. Isolating external dependencies from your tests • “Mocking” @brianbunke
10. How would you prepare to give a presentation? @brianbunke
11. DEMO Integration Test to Unit Test Mock 101 @brianbunke
12. Don’t Fall in Love on the First Date
13. 2 Unit Tests, 0 Integration Tests @brianbunke
14. Integration Tests -- We’re Still Friends! You should know if an API has changed …eventually Limit, don’t eliminate @brianbunke
15. Unit Test “Drawback” #1: Testable Code Mocking works with functions (and modules) Writing tests makes you write more testable code @brianbunke
16. DEMO Keep your code testable One function = one purpose @brianbunke
17. Unit Test Drawback #2: Parameter Types If unit testing isolates third-party dependencies, strongly typing our parameters is an issue @brianbunke
18. DEMO Isolate third-party dependencies to private functions @brianbunke
19. Unit Test Drawback #3: “Tryhard” Mode Strive for “black box” over “white box” Tests are meant to help maintain and refactor Accept that bugs will always exist @brianbunke
20. DEMO Unit testing our new module’s functions Using Mock -ParameterFilter @brianbunke
21. Limitations of ParameterFilter Mocks • Parameters must be explicitly named • Common names may collide with Pester internals • Use $PSBoundParameters instead @brianbunke
22. Unit Test Drawback #4: Consistency Unit tests are optimistic about breaking changes, but we also need to look inward. @brianbunke
23. Consistency Tests Large pull requests happen Human code reviews are fallible @brianbunke
24. Negative Tests @brianbunke
25. DEMO oops Because you should say “oops” before you deploy, not after @brianbunke
26. Making Your Love Last @brianbunke
27. How Can You Love Unit Tests? @brianbunke
28. How Can You Love Unit Tests? Write as few of them as possible. @brianbunke
29. How Can You Love Unit Tests? •Trust is freeing •Fast •Independent •Repeatable @brianbunke
30. How to Keep Loving Unit Tests • Single responsibility functions • Strongly typing parameters from dependencies? • Push everything possible toward the module level • When in doubt, keep it simple • Consider Test-Driven Development (TDD) @brianbunke
31. xUnit Test Patterns Gerard Meszaros Practical Test Pyramid https://martinfowler.com/ articles/practical-test-pyramid.html @brianbunke
32. Pester Resources https://github.com/pester/Pester/wiki @brianbunke
33. PowerShell Summit Resources • Today’s talk • https://github.com/brianbunke/PesterUnitTesting2018 • 2018, Glenn Sarti • https://speakerdeck.com/glennsarti • 2017, Chris Hunt • https://github.com/cdhunt/pssummit2017-mocking • 2016, June Blender • https://youtu.be/jvvh9cpD_LM @brianbunke
34. THANK YOU! Please use the event app or Sched.com to submit a session rating! @brianbunke brianbunke.com speakerdeck.com/brianbunke