Make your tests tell the story of your domain

Even with perfect naming and perfect code, it is hard to read the story of your domain straight out of it. You can be certain that you’ll have forgotten some of the nuances about the code the next time you see it. Or someone else sees it, because very few of us live our professional coding lives in an area where it’s only me ever handling the code. Someone is going to come back to your code - in five days, three months or five years.

Luckily, if you write your tests the right way, they can tell the story of your domain in a way your production code can't. Let us show you how to create your tests so you can get rid of your stale documentation.

Co-presentation with Anne Landro.

Transcript

1. Make your tests tell the story of your domain Anne Landro @AnneLandro Mads Opheim @MadsOpheim DDD Europe
2. Did you know that a property can own itself? 2
3. A project named Lovisa 3
4. A long time ago in a Lovisa far, far away 4
5. We don’t like testing 5
6. We don’t like testing manual verification 6
7. Use your computer 7
8. Don’t Repeat Yourself 8
9. Why do we write tests? 9
10. Not all tests are created equal! 10
11. What story do you want to tell? 11
12. Tell the whole story 12
13. What happens when you die? 13
14. 14 PersonIsRegisteredAsDeadAfterStartOfACaseOfDeath: createACaseOfDeath() registerTheDiseased() registerTheHeirs() notifyTheNationalRegistryOfTheDeath() assertThatThePersonIsRegisteredAsDead()
15. One test, several wins 15
16. But that’s not all 16
17. Value chain your unhappy paths 17
18. 18 courtWillContactYou: writeALetterToSend() sendLetterByMail() receiveAnswer() assertThatYouHaveConfirmedToReceiveTheLetter()
19. 19 courtWillDoSeveralAttemptsToContactYou: writeALetterToSend() sendLetterByMail() waitTwoWeeksForAnswer() sendThePoliceToYourDoorToGiveYouTheLetterInPerson() assertThatYouHaveConfirmedToReceiveTheLetter()
20. Tell the quirks of the domain 20 Test rare occurences
21. This one took down the system 21
22. 22 Test Obscure Scenario That Happens In Production Where A Property Owns Itself()
23. 23 Test Specific Case In Oslo Where The Property Has No Owners()
24. What is a domain? 24
25. What is the technical domain? 25
26. Different domains, different languages 26
28. Tell the technical details 28
29. SearchForHouseTest.java RegisterHouseTest.java MatrikkelFacadeTest.java 29
31. Tell the business details 31
32. 32 Contact Every Part In The Claim But Not The Ones Who Sent It in()
33. Tests are as important as production code 33
34. Production code solves problems, test code visualizes them 34
35. Tests are a swiss army knife 35
36. Tell the story bearing in mind that you’ll forget things 36
37. Naming tests 37
38. How to know if your test name ain’t good? 38
39. 39 The Deadline For Kunngjøring Is Four Weeks()
40. 40 Properties For Namsmann Mainly Follow The Same Rules as Hovedstevnevitne()
41. Don’t tell lies 41
42. 42 The Deadline For Kunngjøring Is Four Weeks()
43. Use real mocks 43
46. Beware the copy-paste fallacy 46
47. Typing prevents domain lies 47
48. Mob testing 48
49. Mob testing – fun for the whole team(?) 49
50. Long story short 50
51. 51 The property that owns itself
52. Dank je! @MadsOpheim mads.opheim@computas.com @AnneLandro anne.landro@computas.com 52