TDD Kata

Kata

• A form, a practice, a try
• Small word problem made to be solved as a method of introspection
• A place to exaggerate a methodology in order to practice the craft

Step Size

• One Test at a Time
• Smallest Test you can possibly think of
• Only the code to pass the test

Step Size

class TddBasics {

    @Test
    fun firstTest() {
        assertEquals(2, sum(1, 1))
    }
}

fun sum(a: Int, b: Int): Int {
}

Step Size

class TddBasics {

    @Test
    fun firstTest() {
        assertEquals(2, sum(1, 1))
    }
}

fun sum(a: Int, b: Int): Int {
    return 2
}

Step Size

class TddBasics {

    @Test
    fun firstTest() {
        assertEquals(2, sum(1, 1))
    }

    @Test
    fun secondTest() {
        assertEquals(4, sum(1, 3))
    }
}

fun sum(a: Int, b: Int): Int {
    return a + b
}

Pairing

• A writes a test
• B passes the test
• B writes the next test
• A passes the test
• Repeat

Commits

• Write one commit per test
• Write a good commit message
  • A good commit message is in the present imperative. It tells what the patch does to the code base
    • Instead of “I walked the dog”, write “Walk the dog”
  • Not what you did, but why you did it
    • Instead of “Add five to tax calculation”, write “Account for base tax amount”

Refactoring

• Red, Green, Refactor
• Not done every test, but should be considered every test
• Should not change existing tests, 90% of the time
  • Changing tests indicates that the tests are too much at implementation level
• Should NEVER add new tests or functionality during this stage
• If you’re newer to TDD, it’s better to skip this then to fall into using this as an escape hatch to not do TDD

Points

• Not a competition…. But if it were…
• If I wrote a smaller test, I get more points
• If I wrote less code to make it pass, I get more points
• If I added functionality not needed for the test, I lose points
• If I am clever and accomplish two things at once, I lose points
• How literally can you do the instructions? How anal can you be?
• This is the time to over exaggerate so you get practice.

Redundant Repetition

• Every time I explain this to someone they nod… and then they write multiple tests or implementation in one commit. Don’t fall into that trap!
• The point is to be anal, if you’re thinking you’re being clever by skipping steps, you’re just cheating yourself!

An Opportunity for Review

• If you’d like me to take a look at your kata when you’re done, shoot me a link to the repo and I’ll spend some time and give you feedback. :)