Too many mocks killed the test - Sw Crafters Lyon 2021

Meetup : https://www.meetup.com/fr-FR/Software-Craftsmanship-Lyon/events/277307036/

Github demo project : https://github.com/JMLamodiere/tdd-demo-swcraftlyon-scala

Transcript

1. Too many mocks killed the test What Hexagonal Architecture has changed Icons made by Icongeek26, Freepik from www.flaticon.com Jean-Marie Lamodière - Backend tech lead @jmlamodiere @swcraftlyon Slow Fast, Focus
2. WHY ? Locking Tests vs. TDD Development Locking Tests Development TDD +50% Icons made by Roundicons from www.flaticon.com “I mock almost nothing” - Kent Beck https://youtu.be/z9quxZsLcfo?t=1270
3. WHY ? Kurt Lewin Change Theory https://sanzubusinesstraining.com/kurt-lewin-change-model/ “...but everyone test like that” - Your colleagues
4. WHY ? Icons made by Freepik from www.flaticon.com Refactor locking tests https://github.com/JMLamodiere/tdd-demo-forumphp2020 POO, sync 2 demo projects Tests first https://github.com/JMLamodiere/tdd-demo-swcraftlyon-scala POO, async
5. WHY ? Icons made by Freepik from www.flaticon.com https://github.com/JMLamodiere/tdd-demo-forumphp2020 /Application /Command RegisterRunningSession RegisterRunningSessionHandler /Domain WeatherProvider(Interface) RunningSession RunningSessionRepo(Interface) /Infrastructure /Http HttpAccuWeatherProvider CurrentConditionDeserializer /Database PostgresRunningSessionRepo /Infrastructure /Symfony RunningSessionController RegisterRunningSessionDeserializer RunningSessionSerializer Technical Business Technical
6. WHY ? Icons made by Freepik from www.flaticon.com https://github.com/JMLamodiere/tdd-demo-swcraftlyon-scala /Application /Command RegisterRunningSession RegisterRunningSessionHandler /Domain WeatherProvider(Interface) RunningSession RunningSessionRepo(Interface) /Infrastructure /Http HttpAccuWeatherProvider /Database PostgresRunningSessionRepo /Infrastructure /AkkaHttp RunningSessionPostController JsonSupport Technical Business Technical
7. WHY ? ...But that’s DDD? No it’s hexagonal! https://afup.org/talks/3037-de-crud-a-ddd-comment-meetic-a-sauve-son-legacy 4k vues 😱
8. • A Functional Test describes a behaviour • A Unit Test locks an implementation Prejudice #1 Icons made by Freepik from www.flaticon.com Could you review my PR before I write my Unit Tests ?
9. • A Functional Test describes a behaviour • A Unit Test locks an implementation Prejudice #1 Icons made by Roundicons from www.flaticon.com All tests describe an expected public behaviour Only the audience and the size of the covered area vary Test Desiderata - Kent Beck : https://kentbeck.github.io/TestDesiderata/
10. “Unit Test” = 1 method of 1 class Prejudice #2 Icons made by Freepik from www.flaticon.com
11. “Unit Test” = 1 method of 1 class Prejudice #2 Icons made by Roundicons, Smashicons from www.flaticon.com Polysemy! Wrong debate... “A DeveloperTest is the correct name for what the industry generally calls a UnitTest” - Ward Cunningham The Unit Test trap : https://drpicox.medium.com/the-unit-test-trap-4a83e4012b17
12. • Test Pyramid = big Unit Test coverage • Unit Test = mock other classes Prejudice #3 Icons made by Freepik from www.flaticon.com
13. • Test Pyramid = big Unit Test coverage • Unit Test = mock other classes Prejudice #3 Icons made by Roundicons, Smashicons from www.flaticon.com Favor fast and focused tests. Ex: The Practical Test Pyramid : https://martinfowler.com/articles/practical-test-pyramid.html Slow Fast, Focus Sociable Unit Test UI component test Unit Tests on Adapters
14. Only functional tests have 3 steps: • Given • When • Then Prejudice #4 Icons made by Freepik from www.flaticon.com
15. Only functional tests have 3 steps: • Given • When • Then Prejudice #4 Icons made by Roundicons from www.flaticon.com All tests follow the narrative structure: • Given = Arrange • When = Act • Then = Assert Setup Catalyst Resolution
16. Prejudice #5 Icons made by Freepik from www.flaticon.com Checking the number of calls to all mocked methods increases my confidence. ->expects($this->exactly(1))->method('xxx') ->shouldBeCalledTimes(1)
17. Prejudice #5 Checking the number of calls to all mocked methods increases my confidence ->expects($this->exactly(1))->method('xxx') ->shouldBeCalledTimes(1) Icons made by Roundicons, Smashicons from www.flaticon.com • Blurs the intent of the test • Locks implementation details • Impossible to write first
18. WHY ? What to test ? Subject Under Test (S.U.T.) Arguments (IN) Return value (OUT) Test Calls Collaborator (IN) Collaborator (OUT) Assert Stub : willReturn() Spy : shouldHaveBeenCalled() Given When Then Then
19. I must know the splitting between my classes before I write my tests Prejudice #6 Icons made by Freepik from www.flaticon.com
20. I must know the splitting between my classes before I write my tests Prejudice #6 Icons made by Roundicons from www.flaticon.com • Prod classes splitting != test classes splitting • Start with an area with a known boundary
21. WHY ? Icons made by Freepik from www.flaticon.com /Application /Command RegisterRunningSession RegisterRunningSessionHandler /Domain WeatherProvider(Interface) RunningSession RunningSessionRepo(Interface) /Infrastructure /Http HttpAccuWeatherProvider CurrentConditionDeserializer /Database PostgresRunningSessionRepo /Infrastructure /Symfony RunningSessionController RegisterRunningSessionDeserializer RunningSessionSerializer Technical Business Technical 1st test: area with a known boundary
22. Prejudice #7 Icons made by Freepik from www.flaticon.com If I don't mock my Entities / DTOs, too many tests will break if I add a field
23. Prejudice #7 Icons made by Roundicons from www.flaticon.com If I don't mock my Entities / DTOs, too many tests will break if I add a field • Use test Factori(es) with optional fields • Getter not covered ? I remove it
24. Prejudice #8 Icons made by Freepik from www.flaticon.com I can mock the libraries used on the Infrastructure side : • Http : Guzzle… • Database : Doctrine, Eloquent…
25. Prejudice #8 Icons made by Roundicons, Smashicons from www.flaticon.com I can mock the libraries used on the Infrastructure side : • Http : Guzzle… • Database : Doctrine, Eloquent… • Coupled with the usage details of the lib • Assumptions about the way it behaves • Impossible to write first • No confidence when upgrading the lib
26. WHY ? Infrastructure : Integration Tests Icons made by Freepik, Smashicons, Roundicons from www.flaticon.com QueryBuilder -> pure SQL MysqlRepository Docker mysql HttpRepository Wiremock Guzzle -> Symfony HttpClient Refactoring eg.
27. WHY ? “Don’t mock what you don’t own” Icons made by Freepik, Smashicons, Roundicons from www.flaticon.com /Application /Command RegisterRunningSession RegisterRunningSessionHandler /Domain WeatherProvider(Interface) RunningSession RunningSessionRepo(Interface) /Infrastructure /Http HttpAccuWeatherProvider CurrentConditionDeserializer /Database PostgresRunningSessionRepo Unit/Fast/Small tests Integration Mock No Mock!
28. Prejudice #9 Icons made by Freepik from www.flaticon.com Functional Test = necessarily end to end
29. Prejudice #9 Icons made by Roundicons, smashicons from www.flaticon.com Functional Test = necessarily end to end • Slow • Brittle • Difficult to maintain • Harder to write first • Locks Infrastructure choices too soon Suggestion : mock Secondary Ports
30. WHY ? Icons made by Freepik from www.flaticon.com /Application /Command RegisterRunningSession RegisterRunningSessionHandler /Domain WeatherProvider(Interface) RunningSession RunningSessionRepo(Interface) /Infrastructure /Http HttpAccuWeatherProvider CurrentConditionDeserializer /Database PostgresRunningSessionRepo /Infrastructure /Symfony RunningSessionController RegisterRunningSessionDeserializer RunningSessionSerializer Suggestion Functional Integration
31. WHY ? Icons made by Freepik from www.flaticon.com Suggestion Functional Integration Outside-in Diamond 🔷 TDD - Thomas Pierrain http://tpierrain.blogspot.com/2021/03/outside-in-diamond-tdd-1-style-made.html
32. @jmlamodiere Thanks! Development Locking tests Development TDD +50% Icons made by Roundicons, Freepik from www.flaticon.com It’s your turn ! • //Given //When //Then • Even if I write a test afterwards, I only write what I would have been sure of before https://github.com/JMLamodiere/tdd-demo-forumphp2020 https://github.com/JMLamodiere/tdd-demo-swcraftlyon-scala @swcraftlyon