Intro and Presentation - TDD in Kotlin by Ian Brandt

Intro and presentation slides for SD Kotlin's August 2018 meeting.

Transcript

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2. San Diego Kotlin User Group
   www.meetup.com/sd-kotlin
   www.linkedin.com/company/sd-kotlin
   github.com/sdkotlin
   @sdkotlin on Twitter, Facebook, and Instagram
   #san-diego on kotlinlang.slack.com
   

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3. Our Mission
   Advancing the Kotlin programming community
   in San Diego, and beyond.
   

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4. Raffle!
   $1
   

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5. A word from our sponsors...
   

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6. Forging STEM pioneers
   https://www.brandt.academy/
   

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10. Call for Presenters
    Get your 15, 30, 45+ minutes of fame by sharing your
    favorite Kotlin-related whatever!
    

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11. Call for Sponsors
    Get your name up in lights, and the eternal gratitude of San
    Diego’s Kotlin engineers!
    

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12. Announcements?
    ● Hiring?
    ● Looking for work?
    ● Other meetups?
    

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13. Dana Gibson
    ● Rocking his Kotlin shirt at the Neil Young concert
    

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14. Kotlin News
    ● Kotlin 1.3 M1!
    ○ Coroutines graduating to stable
    ○ Assignment of when subject to variable
    ○ Unsigned integer types and arithmetic
    ○ Function types with 255 parameters
    ○ Multiplatform Random API
    ○ Companion object for Boolean
    

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15. Try Kotlin Online
    https://try.kotlinlang.org/
    

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16. Let’s slack off!
    http://slack.kotlinlang.org/
    #san-diego
    

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17. TDD in Kotlin
    Ian Brandt
    

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18. A Set of Unit Test Rules
    A test is not a unit test if:
    ● It talks to the database
    ● It communicates across the network
    ● It touches the file system
    ● It can't run at the same time as any of your other unit tests
    ● You have to do special things to your environment (such as editing config
    files) to run it
    

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19. Test and Assertion Frameworks
    ● Mostly as in Java
    ○ JUnit
    ○ TestNG
    ○ AssertJ
    ○ Mockito
    

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20. Test and Assertion Frameworks
    ● Kotlin-specific frameworks evolving
    ○ Mockk
    ○ Atrium
    ○ KotlinTest
    ○ Spek
    ○ kotlin.test
    

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21. The Cycles of TDD
    ● The Three Laws of TDD (seconds)
    ● The Red-Green-Refactor Cycle (minutes)
    ● The Specific/Generic Cycle (deca-minutes)
    ● The Architectural Boundaries Cycle (hours)
    

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22. The Three Laws of TDD
    Second-by-Second
    ● Thou shalt not write any production code without first
    writing a failing unit test
    ● Thou shalt not write any more of a unit test than is
    necessary to fail (and not compiling is failing)
    ● Thou shalt not write any more production code than is
    needed to make the most recent failing unit test pass
    

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23. The Red-Green-Refactor Cycle
    Minute-by-Minute
    ● Get RED
    ○ Just focus on the next test.
    ● Get GREEN
    ○ Just focus on the simplest way to make that test
    pass. Don’t worry about refactoring!
    ● Now REFACTOR
    ○ Keep the same tests passing
    

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24. The Specific/Generic Cycle
    ~Ten Minutes
    ● As the tests get more specific, the code gets more
    generic
    ○ I.e. if your next test drives the code to be more
    specific, maybe you picked the wrong next test
    ○ You’ll know if you get stuck
    

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25. The Architecture Boundaries Cycle
    Hour-by-Hour
    ● Pause to consider whether you’re evolving clean
    architecture
    ○ Are you Red-Green-Refactoring your way to a
    monolith?
    ● Refactor as needed with your awesome suite of
    super-fast unit tests
    

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26. The Transformation Priority Premise
    ● Refactoring: Changing the structure of code without
    changing its behavior
    ● Transforming: Changing the behavior
    

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27. The Transformation Priority Premise
    1. ({} → nil) no code at all → code that employs nil
    2. (nil → constant)
    3. (constant → constant+) a simple constant to a more complex constant
    4. (constant → scalar) replacing a constant with a variable or an argument
    5. (statement → statements) adding more unconditional statements.
    6. (unconditional → if) splitting the execution path
    7. (scalar → array)
    8. (array → container)
    9. (statement → tail-recursion)
    10. (if → while)
    11. (statement → non-tail-recursion)
    12. (expression → function) replacing an expression with a function or algorithm
    13. (variable → assignment) replacing the value of a variable.
    14. (case) adding a case (or else) to an existing switch or if
    

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28. Let’s code!
    

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