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
   

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2. Did you know
   that a property
   can own itself?
   2
   

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3. A project named
   Lovisa
   3
   

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4. A long time ago in a
   Lovisa far, far away
   4
   

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5. We don’t like testing
   5
   

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6. We don’t like testing
   manual verification
   6
   

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7. Use your computer
   7
   

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8. Don’t
   Repeat
   Yourself
   8
   

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9. Why do we write tests?
   9
   

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10. Not all tests are
    created equal!
    10
    

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11. What story do you
    want to tell?
    11
    

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12. Tell the whole story
    12
    

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13. What happens when
    you die?
    13
    

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14. 14
    PersonIsRegisteredAsDeadAfterStartOfACaseOfDeath:
    createACaseOfDeath()
    registerTheDiseased()
    registerTheHeirs()
    notifyTheNationalRegistryOfTheDeath()
    assertThatThePersonIsRegisteredAsDead()
    

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15. One test, several wins
    15
    

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16. But that’s not all
    16
    

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17. Value chain your
    unhappy paths
    17
    

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18. 18
    courtWillContactYou:
    writeALetterToSend()
    sendLetterByMail()
    receiveAnswer()
    assertThatYouHaveConfirmedToReceiveTheLetter()
    

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19. 19
    courtWillDoSeveralAttemptsToContactYou:
    writeALetterToSend()
    sendLetterByMail()
    waitTwoWeeksForAnswer()
    sendThePoliceToYourDoorToGiveYouTheLetterInPerson()
    assertThatYouHaveConfirmedToReceiveTheLetter()
    

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20. Tell the quirks of the
    domain
    20
    Test rare occurences
    

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21. This one took
    down the
    system
    21
    

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22. 22
    Test Obscure Scenario That Happens In Production
    Where A Property Owns Itself()
    

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23. 23
    Test Specific Case In Oslo Where The Property Has No
    Owners()
    

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24. What is a domain?
    24
    

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25. What is the technical
    domain?
    25
    

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26. Different domains,
    different languages
    26
    

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28. Tell the technical
    details
    28
    

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29. SearchForHouseTest.java
    RegisterHouseTest.java
    MatrikkelFacadeTest.java
    29
    

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31. Tell the business
    details
    31
    

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32. 32
    Contact Every Part In The Claim But Not The Ones Who
    Sent It in()
    

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33. Tests are as important
    as production code
    33
    

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34. Production code
    solves problems,
    test code
    visualizes them
    34
    

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35. Tests are a swiss army knife
    35
    

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36. Tell the story bearing
    in mind that you’ll
    forget things
    36
    

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37. Naming tests
    37
    

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38. How to know if your
    test name ain’t good?
    38
    

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39. 39
    The Deadline For
    Kunngjøring Is Four Weeks()
    

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40. 40
    Properties For Namsmann
    Mainly Follow The Same
    Rules as Hovedstevnevitne()
    

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41. Don’t tell lies
    41
    

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42. 42
    The Deadline For
    Kunngjøring Is Four Weeks()
    

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43. Use real mocks
    43
    

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46. Beware the copy-paste
    fallacy
    46
    

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47. Typing prevents
    domain lies
    47
    

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48. Mob testing
    48
    

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49. Mob testing – fun for
    the whole team(?)
    49
    

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50. Long story short
    50
    

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51. 51
    The property
    that owns itself
    

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52. Dank je!
    @MadsOpheim
    mads.opheim@computas.com
    @AnneLandro
    anne.landro@computas.com
    52
    

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