Building Robust Software, Episode 3

Presented at https://www.meetkt.org on 17 December 2021

This episode explains how the design of the production code can affect the maintenance of tests. We also touch upon different kinds of testing tools and methodologies suited for various software development and maintenance scenarios.

Transcript

1. Ragunath Jawahar • @ragunathjawahar • https://ragunath.xyz
   Building Robust Software
   Episode 3: Not going to convince you to write tests
   

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2. 
   

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3. Episode 1: Small ideas, big impact
   • Robustness principle & a tweaked version of it
   
   • Algebraic data types
   
   • Total & partial functions
   
   • Minimising defensive programming
   
   • Using the type system to short-circuit failures (a.k.a failing fast)
   
   • Avoiding primitive obsession
   

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4. Episode 2: Exceptions, side-effects and boundaries
   • Exception anti-patterns
   
   • Handling
   
   • Throwing
   
   • Tester-Doer pattern
   
   • Try-Parse Pattern
   
   • Converting exceptions to values
   
   • Introduction to values as boundaries
   
   • Architectures that use values as boundaries
   

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5. Building Robust Software Playlist
   https://bit.ly/3F2ijgm
   

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6. <
   /
   recap>
   

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7. Why this talk?
   

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8. Scenario
   An event management startup has hired you and needs your help to build a
   feature that sends reminder emails to potential attendees for an upcoming
   event.
   

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9. class EventManager(
   
   
   private val dao: EventDao,
   
   
   private val mailer: Mailer
   
   
   ) {
   
   
   fun sendReminder(event: Event) {
   
   
   val registrants = dao.getRegistrants(event.id)
   
   
   val potentialAttendees = registrants
   
   
   .filter { it.rsvp
   ==
   YES
   ||
   it.rsvp
   =
   =
   MAYBE }
   
   
   potentialAttendees.onEach { attendee
   ->
   
   
   mailer.mail(attendee.emailAddress, event.reminder)
   
   
   }
   
   
   }
   
   
   }
   a.EventManager.kt
   

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10. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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11. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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12. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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13. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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14. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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15. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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16. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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17. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

18. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

19. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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20. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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21. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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22. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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23. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

24. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

25. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

26. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

27. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

28. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

29. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

30. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

31. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

32. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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33. Scenario
    Your company is losing money 💸 💸 💸 due to bug
    fi
    xes in production, so
    your team has decided to write tests. It's your responsibility to bring your
    modules under test.
    

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34. 🤔
    

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35. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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36. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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37. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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38. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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39. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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40. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

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41. Test: No registrations
    

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42. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

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43. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

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44. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

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45. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

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46. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

47. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

48. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

49. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

50. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

51. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

52. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

53. @Test
    
    
    fun `don't send emails when there are no registrants`() {
    
    
    //
    given
    
    
    val dao = mock()
    
    
    val mailer = mock()
    
    
    val eventManager = EventManager(dao, mailer)
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(emptyList())
    
    
    val event = Event(
    
    
    "Building Robust Software III",
    
    
    "Event is on 16th December, please attend."
    
    
    )
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verifyNoInteractions(mailer)
    
    
    }
    

    View Slide

54. Test: A mix of “Yes”, “No” and
    “Maybe”
    

    View Slide

55. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

56. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

57. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

58. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

59. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

60. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

61. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

62. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

63. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

64. @Test
    
    
    fun `email only those who RSVP'd yes and maybe`() {
    
    
    //
    given
    
    
    val allRegistrants = listOf(
    
    
    User("yes@example.com", Rsvp.YES),
    
    
    User("no@example.com", Rsvp.NO),
    
    
    User("maybe@example.com", Rsvp.MAYBE)
    
    
    )
    
    
    whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
    
    
    //
    when
    
    
    eventManager.sendReminder(event)
    
    
    //
    then
    
    
    verify(mailer).mail("yes@example.com", event.reminder)
    
    
    verify(mailer).mail("maybe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    
    
    }
    

    View Slide

65. ✅ No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    ✅ A mix of “Yes”, “No” and “Maybe”
    

    View Slide

66. Behaviour testing
    

    View Slide

67. Event
    Manager
    Event
    
    
    Dao
    Mailer
    

    View Slide

68. Event
    Manager
    Event
    
    
    Dao
    Mailer
    System under test (SUT)
    

    View Slide

69. Event
    Manager
    Event
    
    
    Dao
    Mailer
    Collaborators
    

    View Slide

70. Collaborators
    • Real thing
    
    • Sorta real thing
    

    View Slide

71. Sorta real thing
    • Stubs
    
    • Mocks
    
    • Fakes
    
    • Dummies
    
    • Spies
    https://martinfowler.com/articles/mocksArentStubs.html
    

    View Slide

72. Current EventManager design
    • Encapsulates business logic
    
    • Who should be noti
    fi
    ed?
    

    View Slide

73. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

74. Current EventManager design
    • Encapsulates business logic
    
    • Who should be noti
    fi
    ed?
    • Coordination logic
    
    • Who is talking to who?
    

    View Slide

75. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    ||
    it.rsvp
    =
    =
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    a.EventManager.kt
    

    View Slide

76. Current EventManager design
    • Encapsulates business logic
    
    • Who should be noti
    fi
    ed?
    • Coordination logic
    
    • Who is talking to who?
    

    View Slide

77. Testing the business logic
    

    View Slide

78. Testing the business logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

79. Testing the business logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

80. Testing the business logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

81. Testing the business logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

82. Testing the business logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

83. Testing the coordination logic
    

    View Slide

84. Testing the coordination logic
    verifyNoInteractions(mailer)
    verify(mailer).mail("jane@example.com", event.reminder)
    
    
    verify(mailer).mail("joe@example.com", event.reminder)
    
    
    verifyNoMoreInteractions(mailer)
    

    View Slide

85. Do-Over
    

    View Slide

86. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .potentialAttendees()
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    | |
    it.rsvp
    ==
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    

    View Slide

87. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .potentialAttendees()
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    | |
    it.rsvp
    ==
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    

    View Slide

88. class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .potentialAttendees()
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .filter { it.rsvp
    ==
    YES
    | |
    it.rsvp
    ==
    MAYBE }
    
    
    potentialAttendees.onEach { attendee
    ->
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    

    View Slide

89. b.EventManager.kt
    class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .potentialAttendees()
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    

    View Slide

90. b.EventManager.kt
    class EventManager(
    
    
    private val dao: EventDao,
    
    
    private val mailer: Mailer
    
    
    ) {
    
    
    fun sendReminder(event: Event) {
    
    
    val registrants = dao.getRegistrants(event.id)
    
    
    val potentialAttendees = registrants
    
    
    .potentialAttendees()
    
    
    potentialAttendees.onEach { attendee
    ->
    
    
    mailer.mail(attendee.emailAddress, event.reminder)
    
    
    }
    
    
    }
    
    
    }
    

    View Slide

91. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

92. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

93. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

94. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

95. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

96. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

97. Users.kt
    fun List.potentialAttendees(): List =
    
    
    this.filter { user
    ->
    user.rsvp
    =
    =
    Rsvp.YES
    |
    |
    user.rsvp
    ==
    Rsvp.MAYBE }
    

    View Slide

98. No registrations
    Everyone RSVP’d “Yes”
    Everyone RSVP’d “No”
    Everyone RSVP’d “Maybe”
    A mix of “Yes”, “No”, and “Maybe”
    

    View Slide

99. Test: No registrations
    

    View Slide

100. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

101. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

102. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

103. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

104. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

105. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

106. @Test
     
     
     fun `no potential attendees for an empty list`() {
     
     
     //
     given
     
     
     val noRegistrants = emptyList()
     
     
     //
     when
     
     
     val potentialAttendees = noRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     
     
     }
     

     View Slide

107. Test: A mix of “Yes”, “No” and
     “Maybe”
     

     View Slide

108. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

109. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

110. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

111. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

112. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

113. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

114. @Test
     
     
     fun `potential attendees contains only registrants those who RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     

     View Slide

115. ✅ No registrations
     Everyone RSVP’d “Yes”
     Everyone RSVP’d “No”
     Everyone RSVP’d “Maybe”
     ✅ A mix of “Yes”, “No” and “Maybe”
     

     View Slide

116. 🤨
     

     View Slide

117. Value testing
     

     View Slide

118. I O
     

     View Slide

119. I O
     Input
     

     View Slide

120. I O
     Output
     

     View Slide

121. I O
     System under test (SUT)
     

     View Slide

122. Collaborators
     • None
     
     • We use real things
     

     View Slide

123. Newer EventManager design
     • Does not encapsulate business logic
     
     • Can use micro unit tests to test various cases
     
     • Value-in, value-out results in decoupled design
     
     • No dependencies for business logic
     

     View Slide

124. Testing the business logic
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     

     View Slide

125. Testing the business logic
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     

     View Slide

126. Testing the business logic
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     

     View Slide

127. Testing the business logic
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     

     View Slide

128. Testing the business logic
     assertThat(potentialAttendees)
     
     
     .isEmpty()
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     

     View Slide

129. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

130. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

131. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

132. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

133. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

134. Testing the coordination logic
     @Test
     
     
     fun `query and email folks who RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     
     
     

     View Slide

135. Implementation A vs. B
     @Test
     
     
     fun `RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     @Test
     
     
     fun `RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     

     View Slide

136. Implementation A vs. B
     @Test
     
     
     fun `RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     @Test
     
     
     fun `RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     

     View Slide

137. Implementation A vs. B
     @Test
     
     
     fun `RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     @Test
     
     
     fun `RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     

     View Slide

138. Implementation A vs. B
     @Test
     
     
     fun `RSVP'd yes or maybe`() {
     
     
     //
     given
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     //
     when
     
     
     val potentialAttendees = allRegistrants.potentialAttendees()
     
     
     //
     then
     
     
     assertThat(potentialAttendees)
     
     
     .containsExactly(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     }
     @Test
     
     
     fun `RSVP'd yes and maybe to the event`() {
     
     
     //
     given
     
     
     val dao = mock()
     
     
     val mailer = mock()
     
     
     val eventManager = EventManager(dao, mailer)
     
     
     val event = Event(
     
     
     1,
     
     
     "Building Robust Software III",
     
     
     "Event is on 16th December, please attend."
     
     
     )
     
     
     val allRegistrants = listOf(
     
     
     User("yes@example.com", Rsvp.YES),
     
     
     User("no@example.com", Rsvp.NO),
     
     
     User("maybe@example.com", Rsvp.MAYBE)
     
     
     )
     
     
     whenever(dao.getRegistrants(event.id)).thenReturn(allRegistrants)
     
     
     //
     when
     
     
     eventManager.sendReminder(event)
     
     
     //
     then
     
     
     verify(mailer).mail("yes@example.com", event.reminder)
     
     
     verify(mailer).mail("maybe@example.com", event.reminder)
     
     
     verifyNoMoreInteractions(mailer)
     
     
     }
     

     View Slide

139. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

140. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

141. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

142. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

143. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

144. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

145. Implementation A vs. B
     import com.google.common.truth.Truth.assertThat
     
     
     import org.junit.jupiter.api.Test
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     import org.junit.jupiter.api.Test
     
     
     import org.mockito.kotlin.mock
     
     
     import org.mockito.kotlin.verify
     
     
     import org.mockito.kotlin.verifyNoInteractions
     
     
     import org.mockito.kotlin.verifyNoMoreInteractions
     
     
     import org.mockito.kotlin.whenever
     
     
     import xyz.ragunath.events.Event
     
     
     import xyz.ragunath.events.EventDao
     
     
     import xyz.ragunath.events.Mailer
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     

     View Slide

146. Implementation A vs. B
     import com.google.common.truth.Truth.assertThat
     
     
     import org.junit.jupiter.api.Test
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     import org.junit.jupiter.api.Test
     
     
     import org.mockito.kotlin.mock
     
     
     import org.mockito.kotlin.verify
     
     
     import org.mockito.kotlin.verifyNoInteractions
     
     
     import org.mockito.kotlin.verifyNoMoreInteractions
     
     
     import org.mockito.kotlin.whenever
     
     
     import xyz.ragunath.events.Event
     
     
     import xyz.ragunath.events.EventDao
     
     
     import xyz.ragunath.events.Mailer
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     

     View Slide

147. Implementation A vs. B
     import com.google.common.truth.Truth.assertThat
     
     
     import org.junit.jupiter.api.Test
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     import org.junit.jupiter.api.Test
     
     
     import org.mockito.kotlin.mock
     
     
     import org.mockito.kotlin.verify
     
     
     import org.mockito.kotlin.verifyNoInteractions
     
     
     import org.mockito.kotlin.verifyNoMoreInteractions
     
     
     import org.mockito.kotlin.whenever
     
     
     import xyz.ragunath.events.Event
     
     
     import xyz.ragunath.events.EventDao
     
     
     import xyz.ragunath.events.Mailer
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     

     View Slide

148. Implementation A vs. B
     import com.google.common.truth.Truth.assertThat
     
     
     import org.junit.jupiter.api.Test
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     import org.junit.jupiter.api.Test
     
     
     import org.mockito.kotlin.mock
     
     
     import org.mockito.kotlin.verify
     
     
     import org.mockito.kotlin.verifyNoInteractions
     
     
     import org.mockito.kotlin.verifyNoMoreInteractions
     
     
     import org.mockito.kotlin.whenever
     
     
     import xyz.ragunath.events.Event
     
     
     import xyz.ragunath.events.EventDao
     
     
     import xyz.ragunath.events.Mailer
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     

     View Slide

149. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

150. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

151. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

152. Implementation A vs. B
     import com.google.common.truth.Truth.assertThat
     
     
     import org.junit.jupiter.api.Test
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     import org.junit.jupiter.api.Test
     
     
     import org.mockito.kotlin.mock
     
     
     import org.mockito.kotlin.verify
     
     
     import org.mockito.kotlin.verifyNoInteractions
     
     
     import org.mockito.kotlin.verifyNoMoreInteractions
     
     
     import org.mockito.kotlin.whenever
     
     
     import xyz.ragunath.events.Event
     
     
     import xyz.ragunath.events.EventDao
     
     
     import xyz.ragunath.events.Mailer
     
     
     import xyz.ragunath.events.Rsvp
     
     
     import xyz.ragunath.events.User
     

     View Slide

153. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

154. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

155. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

156. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

157. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

158. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

159. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

160. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

161. Implementation A vs. B
     • 5 integration tests
     
     • + Dependencies
     
     • ↑ Coupling
     
     • Wider change propagation
     
     • Harder to maintain
     
     • More assertions
     • 5 micro-unit tests
     
     • 1 integration test
     
     • - Dependencies
     
     • ↓ Coupling
     
     • Limited change propagation
     
     • Easier to maintain
     
     • Fewer assertions
     💯
     

     View Slide

162. Destroy All Software—Boundaries
     https://bit.ly/3yuuxvQ
     

     View Slide

163. What did we learn?
     • Behaviour testing
     
     • Value testing
     
     • Micro-unit tests
     
     • Complementary tests
     
     • Integration tests
     

     View Slide

164. Scenario
     You inherit a codebase that does not have any tests, the previous
     developers have left the organisation and you are expected to enhance an
     existing feature.
     

     View Slide

165. package com.gildedrose
     
     
     class GildedRose(var items: Array) {
     
     
     fun updateQuality() {
     
     
     for (i in items.indices) {
     
     
     if (items[i].name
     !=
     "Aged Brie"
     &&
     items[i].name
     ! =
     "Backstage passes to a TAFKAL80ETC concert") {
     
     
     if (items[i].quality > 0) {
     
     
     if (items[i].name
     !=
     "Sulfuras, Hand of Ragnaros") {
     
     
     items[i].quality = items[i].quality - 1
     
     
     }
     
     
     }
     
     
     } else {
     
     
     if (items[i].quality < 50) {
     
     
     items[i].quality = items[i].quality + 1
     
     
     if (items[i].name
     ==
     "Backstage passes to a TAFKAL80ETC concert") {
     
     
     if (items[i].sellIn < 11) {
     
     
     if (items[i].quality < 50) {
     
     
     items[i].quality = items[i].quality + 1
     
     
     }
     
     
     }
     
     
     if (items[i].sellIn < 6) {
     
     
     if (items[i].quality < 50) {
     
     
     items[i].quality = items[i].quality + 1
     
     
     }
     
     
     }
     
     
     }
     
     
     }
     
     
     }
     
     
     if (items[i].name
     !=
     "Sulfuras, Hand of Ragnaros") {
     
     
     items[i].sellIn = items[i].sellIn - 1
     
     
     }
     
     
     if (items[i].sellIn < 0) {
     
     
     if (items[i].name
     !=
     "Aged Brie") {
     
     
     if (items[i].name
     !=
     "Backstage passes to a TAFKAL80ETC concert") {
     
     
     if (items[i].quality > 0) {
     
     
     if (items[i].name
     !=
     "Sulfuras, Hand of Ragnaros") {
     
     
     items[i].quality = items[i].quality - 1
     
     
     }
     
     
     }
     
     
     } else {
     
     
     items[i].quality = items[i].quality - items[i].quality
     
     
     }
     
     
     } else {
     
     
     if (items[i].quality < 50) {
     
     
     items[i].quality = items[i].quality + 1
     
     
     }
     
     
     }
     
     
     }
     
     
     }
     
     
     }
     
     
     }
     

     View Slide

166. Writing tests for code you wrote
     
     
     vs.
     
     
     Writing tests for someone else’s code
     (characterisation tests)
     

     View Slide

167. @Test
     
     
     fun `aged brie`() {
     
     
     //
     given
     
     
     val itemName = "Aged Brie"
     
     
     val sellIns = arrayOf(-1, 0, 1, 5, 6, 7, 10, 11, 12)
     
     
     val qualities = arrayOf(-1, 0, 1, 49, 50, 51)
     
     
     //
     when
     
     
     val function = updateQualityFunction(itemName)
     //
     (Int, Int)
     - >
     String
     
     
     //
     then
     
     
     CombinationApprovals.verifyAllCombinations(function, sellIns, qualities)
     
     
     }
     

     View Slide

168. @Test
     
     
     fun `aged brie`() {
     
     
     //
     given
     
     
     val itemName = "Aged Brie"
     
     
     val sellIns = arrayOf(-1, 0, 1, 5, 6, 7, 10, 11, 12)
     
     
     val qualities = arrayOf(-1, 0, 1, 49, 50, 51)
     
     
     //
     when
     
     
     val function = updateQualityFunction(itemName)
     //
     (Int, Int)
     - >
     String
     
     
     //
     then
     
     
     CombinationApprovals.verifyAllCombinations(function, sellIns, qualities)
     
     
     }
     

     View Slide

169. @Test
     
     
     fun `aged brie`() {
     
     
     //
     given
     
     
     val itemName = "Aged Brie"
     
     
     val sellIns = arrayOf(-1, 0, 1, 5, 6, 7, 10, 11, 12)
     
     
     val qualities = arrayOf(-1, 0, 1, 49, 50, 51)
     
     
     //
     when
     
     
     val function = updateQualityFunction(itemName)
     //
     (Int, Int)
     - >
     String
     
     
     //
     then
     
     
     CombinationApprovals.verifyAllCombinations(function, sellIns, qualities)
     
     
     }
     

     View Slide

170. [-1, -1]
     =>
     [Aged Brie, -2, 1]
     
     
     [-1, 0]
     =>
     [Aged Brie, -2, 2]
     
     
     [-1, 1]
     =>
     [Aged Brie, -2, 3]
     
     
     [-1, 49]
     =>
     [Aged Brie, -2, 50]
     
     
     [-1, 50]
     =>
     [Aged Brie, -2, 50]
     
     
     [-1, 51]
     =>
     [Aged Brie, -2, 51]
     
     
     [0, -1]
     =>
     [Aged Brie, -1, 1]
     
     
     [0, 0]
     =>
     [Aged Brie, -1, 2]
     
     
     [0, 1]
     =>
     [Aged Brie, -1, 3]
     
     
     [0, 49]
     =>
     [Aged Brie, -1, 50]
     
     
     [0, 50]
     =>
     [Aged Brie, -1, 50]
     
     
     [0, 51]
     =>
     [Aged Brie, -1, 51]
     
     
     [1, -1]
     =>
     [Aged Brie, 0, 0]
     
     
     [1, 0]
     =>
     [Aged Brie, 0, 1]
     
     
     [1, 1]
     =>
     [Aged Brie, 0, 2]
     
     
     [1, 49]
     =>
     [Aged Brie, 0, 50]
     
     
     [1, 50]
     =>
     [Aged Brie, 0, 50]
     
     
     [1, 51]
     =>
     [Aged Brie, 0, 51]
     
     
     [5, -1]
     =>
     [Aged Brie, 4, 0]
     
     
     [5, 0]
     =>
     [Aged Brie, 4, 1]
     
     
     [5, 1]
     =>
     [Aged Brie, 4, 2]
     
     
     [5, 49]
     =>
     [Aged Brie, 4, 50]
     
     
     [5, 50]
     =>
     [Aged Brie, 4, 50]
     
     
     [5, 51]
     =>
     [Aged Brie, 4, 51]
     
     
     [6, -1]
     =>
     [Aged Brie, 5, 0]
     
     
     [6, 0]
     =>
     [Aged Brie, 5, 1]
     
     
     [6, 1]
     =>
     [Aged Brie, 5, 2]
     
     
     [6, 49]
     =>
     [Aged Brie, 5, 50]
     
     
     [6, 50]
     =>
     [Aged Brie, 5, 50]
     
     
     [6, 51]
     =>
     [Aged Brie, 5, 51]
     
     
     [7, -1]
     =>
     [Aged Brie, 6, 0]
     
     
     [7, 0]
     =>
     [Aged Brie, 6, 1]
     
     
     [7, 1]
     =>
     [Aged Brie, 6, 2]
     
     
     [7, 49]
     =>
     [Aged Brie, 6, 50]
     
     
     [7, 50]
     =>
     [Aged Brie, 6, 50]
     
     
     [7, 51]
     =>
     [Aged Brie, 6, 51]
     
     
     [10, -1]
     =>
     [Aged Brie, 9, 0]
     
     
     [10, 0]
     =>
     [Aged Brie, 9, 1]
     
     
     [10, 1]
     =>
     [Aged Brie, 9, 2]
     
     
     [10, 49]
     =>
     [Aged Brie, 9, 50]
     
     
     [10, 50]
     =>
     [Aged Brie, 9, 50]
     
     
     [10, 51]
     =>
     [Aged Brie, 9, 51]
     
     
     [11, -1]
     =>
     [Aged Brie, 10, 0]
     
     
     [11, 0]
     =>
     [Aged Brie, 10, 1]
     
     
     [11, 1]
     =>
     [Aged Brie, 10, 2]
     
     
     [11, 49]
     =>
     [Aged Brie, 10, 50]
     
     
     [11, 50]
     =>
     [Aged Brie, 10, 50]
     
     
     [11, 51]
     =>
     [Aged Brie, 10, 51]
     
     
     [12, -1]
     =>
     [Aged Brie, 11, 0]
     
     
     [12, 0]
     =>
     [Aged Brie, 11, 1]
     
     
     [12, 1]
     =>
     [Aged Brie, 11, 2]
     
     
     [12, 49]
     =>
     [Aged Brie, 11, 50]
     
     
     [12, 50]
     =>
     [Aged Brie, 11, 50]
     
     
     [12, 51]
     =>
     [Aged Brie, 11, 51]
     

     View Slide

171. View Slide

172. Refactor ✌
     

     View Slide

173. View Slide

174. Approval Tests
     • Snapshot testing, golden master testing, etc.,
     
     • Helps bring large portions of code under tests quickly
     
     • Can work on di
     ff
     erent kinds of data
     

     View Slide

175. Approval Tests
     • https://github.com/approvals/ApprovalTests.Java
     
     • https://github.com/approvals/ApprovalTests.Plugins.IntelliJ
     
     • https://github.com/approvals
     

     View Slide

176. More testing tools & techniques
     • Performance testing
     
     • Property testing
     

     View Slide

177. Workflows
     • TDD
     
     • https://www.coderetreat.org/
     
     • TCR
     
     • https://medium.com/@kentbeck_7670/test-commit-revert-870bbd756864
     
     • https://github.com/LarsEckart/tcr-extension
     
     • https://github.com/ragunathjawahar/GildedRose-Refactoring-Kata/tree/rj/
     attempt-04
     

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178. Fin
     Questions?
     @ragunathjawahar • https://ragunath.xyz
     

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