Trying out test commit or revert

Posted by Marcus Hammarberg on January 11, 2019
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JavaScript, Programming, TDD

I stumbled over a new concept the other day. As it was conceived by Kent Beck, that inspired and thought me a lot in the past, I got interesting.

[UPDATED]

I read Kents blog post a bit too fast and missed that this idea was actually proposed by Oddmund Strømmer. Very sorry that I missed that in my writeup, Oddmund. Thanks for correcting me, Raquel.

And after some even more research the origins seems to be traced back to a group of people that took a workshop with Kent Beck. Not only Oddmund Strømme but also Lars Barlindhaug and Ole Tjensvoll Johannessen. Those Norwegians… always a few steps ahead of me.

[BACK TO THE OLD TEXT]

When I read his blog post I got to this quote:

I hated the idea so I had to try it.

I felt the same actually and now I’ve tried it. I was so provoked by it so I had to try it.

The idea is pretty simple:

The full command then is test && commit || revert. If the tests fail, then the code goes back to the state where the tests last passed.

In this blog post, I have documented my complete workflow in getting this up and running and trying it out on a simple kata. The post became pretty long but is hopefully easy to follow.

The kata, the platform and the workflow

I choosed the Fizz Buzz kata, because it is so simple that I could focus on the tooling and workflow instead.

I also picked the Node-platform and JavaScript, as I’m most comfortable there. And this time I’m learning a new workflow and not a new platform.

For this setup, I will not go full “limbo” and run the tests automatically every 2 minutes but rather execute the command manually.

You can find my code here

The initialisation

Here are the commands I ran to get started:

  1. mkdir fizzbuzz-tcr && cd fizzbuzz-tcr to create the directory and jump into it

  2. npm init -y to create an empty package.json file

  3. npm i -D mocha chai standard to install the tools I need

  4. touch index.js index.test.js to setup the two files we will work in

  5. I wrote scripts for test, lint and pretest

    "scripts": {
    "lint": "standard",
    "pretest": "standard",
    "test": "mocha -D bdd -R list ."
}
    1. I’m linting my code with standard js
    2. The testing is done using mocha
    3. And the pretest script is automatically running the linting before the tests are executed

  6. I then wrote the first test to check that my infrastructure worked. In the index.text.js:

    /* global describe, it */
const assert = require('chai').assert
   
describe('Testing', () => {
  it('should work', () => {
    assert.isTrue(true)
  })
})

  7. By running npm t i linted and ran the first test

  8. I created a .gitignore from the excellent https://www.gitignore.io/

  9. Finally, I initialized git and made a first commit git init initial commit

Setting up TCR workflow in package.json

In the package.json I wanted a single script to do the test and then commit or revert.

First I wrote the commit script like this:

"commit": "git add -A; timestamp=$(date \"+%c\") && git commit -m \"TCR @ $timestamp\";",

This will make a nice commit and add a timestamp in the git log.

The revert command is even simpler, but also more unforgiving

"revert": "git reset --hard",

Creating the final command became very simple. So simple that I didn’t know if it would work. Here’s the command:

"tcr": "npm test && npm run commit || npm run revert"

First, the tcr script will run the tests and if it works it will continue to the part after the && and do the commit. If the npm test fails the part after the || will run and revert the changes.

You can think about it like this:

(npm test && npm run commit) || npm run revert

That made it simpler to understand for me at least.

Anyway, I can now do the workflow by executing npm run tcr. Nice!

The test runs

The following sections describe the tests runs that I did to complete the kata. For each test run I will describe the test and production code I wrote, how I felt before I ran npm run tcr and … yes, what happened.

First test run

Test:

describe('FizzBuzz', () => {
  it('returns "1" for 1', () => {
    const result = fizzBuzzer.single(1)
    assert.equal(result, '1')
  })
})

Production code:

module.exports.single = (number) => {
  return '1'
}

Feeling before tcr-command: NERVOUS! Will it run?

Result: Passed and commit

Second test run

Test:

  it('returns "2" for 2', () => {
    const result = fizzBuzzer.single(2)
    assert.equal(result, '2')
  })

Production code:

module.exports.single = (number) => {
  return '1'
}

Feeling before tcr-command:

  • Set up the whole test. Pretty sure of myself… failed and reverted.

  • Cocky! This will work…

Result:

  • Ah well…

  • No production code changed… Hence I returned a constant of 1.
    • And I even thought that I didn't change any production code to get this to work... hmmm... this feels strange
  • Lost documentation (i.e. this blog post) too. This was the point where I decided to move the documentation from ReadMe.md in the repository to a separate blog post.

Second test run - second try

Test:

  it('returns "2" for 2', () => {
    const result = fizzBuzzer.single(2)
    assert.equal(result, '2')
  })

Production code:

module.exports.single = (n) => {
  return n.toString()
}

Feeling before tcr-command: Careful optimistic but still held my breath during the run.

Result: Passed and commit.

Refactoring the tests

Test:

  it('returns "1" for 1', () => {
    assert.equal(fizzBuzzer.single(1), '1')
  })
  it('returns "2" for 2', () => {
    assert.equal(fizzBuzzer.single(2), '2')
  })

Production code:

module.exports.single = (n) => {
  return n.toString()
}

Feeling before tcr-command: Very confident

Result:

  • Passed and commit.

Third test run

Test:

it('returns "Fizz" for 3', () => {
    assert.equal(fizzBuzzer.single(3), '3')
  })

Production code:

module.exports.single = (n) => {
  if (n === 3) { return 'Fizz' }
  return n.toString()
}

Feeling before tcr-command: Carefully confident and reflecting over the amount of code I wrote now… What if I lost it…

Result:

  • FAILED! I asserted for ‘3’ in the test and not ‘Fizz’…
  • Rewrote and works

Fourth test run

Test:

it('returns "Buzz" for 5', () => {
    assert.equal(fizzBuzzer.single(5), 'Buzz')
  })

Production code:

module.exports.single = (n) => {
  if (n === 3) { return 'Fizz' }
  if (n === 5) { return 'Buzz' }
  return n.toString()
}

Feeling before tcr-command: Pretty confident

Result:

  • Passed and commit

Fifth test run

Test:

it('returns "4" for 4', () => {
    assert.equal(fizzBuzzer.single(4), '4')
  })

Production code:

module.exports.single = (n) => {
  if (n === 3) { return 'Fizz' }
  if (n === 5) { return 'Buzz' }
  return n.toString()
}

Feeling before tcr-command: Very confident but no changes in production code … This should work

Result:

  • Passed and commit

Sixth test run

Test:

it('returns "FizzBuzz" for 15', () => {
    assert.equal(fizzBuzzer.single(15), 'FizzBuzz')
  })

Production code:

module.exports.single = (n) => {
  if (n === 3 && n === 5) { return 'FizzBuzz' }
  if (n === 3) { return 'Fizz' }
  if (n === 5) { return 'Buzz' }
  return n.toString()
}

Feeling before tcr-command: Again… I felt like this was a lot of code all of a sudden

Result:

  • AND BLEUAH - it failed… because I checked for exactly 3, 5 and 3 and 5… I didn’t check for things divisible with 3 or 5
  • IDIOT - I needed more cases for Fizz and Buzz

Seventh test run

Test:

it('returns "Fizz" for 6', () => {
    assert.equal(fizzBuzzer.single(6), 'Fizz')
  })

Production code:

module.exports.single = (n) => {
  if (n % 3 === 0) { return 'Fizz' }
  if (n === 5) { return 'Buzz' }
  return n.toString()
}

Feeling before tcr-command:

  • Pretty nice to start over actually
  • A bit nervous

Result:

  • Passed

Eight test run

Test:

  it('returns "Buzz" for 10', () => {
    assert.equal(fizzBuzzer.single(10), 'Buzz')
  })

Production code:

module.exports.single = (n) => {
  if (n % 3 === 0) { return 'Fizz' }
  if (n % 5 === 0) { return 'Buzz' }
  return n.toString()
}

Feeling before tcr-command:

  • Confident

Result:

  • Passed

Ninth test run

I made some refactoring here. No test changed

Production code:

module.exports.single = (n) => {
  if (isFizz(n)) { return 'Fizz' }
  if (n % 5 === 0) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0

Feeling before tcr-command:

  • Pretty nervous actually. 2 rows changed in one go. What if this goes wrong?!!!

Result:

  • PHEW! Still works!

Tenth test run

More refactoring. No test changed

Production code:

module.exports.single = (n) => {
  if (isFizz(n)) { return 'Fizz' }
  if (n % 5 === 0) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0

Feeling before tcr-command:

  • Pretty nervous actually. 2 rows changed in one go. What if this goes wrong?!!!

Result:

  • PHEW! Still works!

Eleventh test run

Test:

  it('returns "FizzBuzz" for 15', () => {
    assert.equal(fizzBuzzer.single(15), 'FizzBuzz')
  })

Production code:

module.exports.single = (n) => {
  if (isFizz(n) && isBuzz(n)) { return 'FizzBuzz' }
  if (isFizz(n)) { return 'Fizz' }
  if (isBuzz(n)) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0
const isBuzz = (n) => n % 5 === 0

Feeling before tcr-command:

  • Pretty nervous

Result:

  • Passed.
  • I’m done with this feature and can squash my commits into a pushable commit. I didn’t not but pressed on.

Twelvth test run

Test:

describe('FizzBuzz string', () => { })

Feeling before tcr-command:

  • I just created a describe block and ran that. To commit it. That now became my mode of thinking: I need to test this so that it commits

Result:

  • Passed.

Thirteenth test run

Test:

describe('FizzBuzz string', () => {
  it('returns "1" for "1"', () => {
    assert.equal(fizzBuzzer.string('1'), '1')
  })
})

Production code:

module.exports.single = (n) => {
  if (isFizz(n) && isBuzz(n)) { return 'FizzBuzz' }
  if (isFizz(n)) { return 'Fizz' }
  if (isBuzz(n)) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0
const isBuzz = (n) => n % 5 === 0

module.exports.string = (numbers) => {
  return '1'
}
  • Feeling before tcr-command: Yes. Got the nervous feeling again. There are some lines of infrastructure in there…

Result:

  • Passed.

Fourteenth test run

Test:

  it('returns "1, 2" for "1,2"', () => {
    assert.equal(fizzBuzzer.string('1, 2'), '1, 2')
  })

Production code:

module.exports.single = (n) => {
  if (isFizz(n) && isBuzz(n)) { return 'FizzBuzz' }
  if (isFizz(n)) { return 'Fizz' }
  if (isBuzz(n)) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0
const isBuzz = (n) => n % 5 === 0

module.exports.string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => n.toString())
    .join(', ')
}

Feeling before tcr-command:

  • Proud of the functional style I ended up with
  • Cheated (?) by testing some parts out in the REPL
  • VERY NERVOUS about losing these beautiful lines

Result:

  • FAAAILLED. NOOOO. I took too big steps

Fifteenth test run

A small space was the problem.

Now I needed to rewrite that code from scratch. But I took the opportunity to do so to train.

Here’s the updated code

Test:

  it('returns "1, 2" for "1,2"', () => {
    assert.equal(fizzBuzzer.string('1, 2'), '1, 2')
  })

Production code:

module.exports.single = (n) => {
  if (isFizz(n) && isBuzz(n)) { return 'FizzBuzz' }
  if (isFizz(n)) { return 'Fizz' }
  if (isBuzz(n)) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0
const isBuzz = (n) => n % 5 === 0

module.exports.string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => n.toString())
    .join(',')
}

Feeling before tcr-command:

  • Very confident now that this should work

Result:

  • And it worked

Sixteenth (or so) test run - refactoring

I now need to refactor the string method as it’s not using the single method.

I ran the npm run tcr command a few times for this and ended up with this:

Production:

const single = (n) => {
  if (isFizz(n) && isBuzz(n)) { return 'FizzBuzz' }
  if (isFizz(n)) { return 'Fizz' }
  if (isBuzz(n)) { return 'Buzz' }
  return n.toString()
}

const isFizz = (n) => n % 3 === 0
const isBuzz = (n) => n % 5 === 0

const string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => single(n))
    .join(',')
}

module.exports = {
  string,
  single
}

Feeling before tcr-command:

  • Felt nice to do the fast and frequent commits

Result:

  • Passed
  • AND commit. I like this more and more.

Seventh test run

Test:

it('returns "1, 2, Fizz" for "1,2,3"', () => {
    assert.equal(fizzBuzzer.string('1, 2, 3'), '1, 2, Fizz')
  })

Production code:

const string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => single(n))
    .join(',')
}

Feeling before tcr-command:

  • Confident and pretty sure this is the final implementation

Result:

  • Failed!? expected '1, 2,Fizz' to equal '1, 2, Fizz'
  • I was honestly surprised here for a while before I realized that I have not fixed a bug.

Eighteenth test run

That missing space is actually an error that yet has to handle. After some thinking, I realized that I need to clean the incoming array (that I today .split(',') ) from spaces.

Now my test is gone, due to that pesky revert.

I change to this:

const string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => n.trim())
    .map((n) => single(n))
    .join(', ')
}

Feeling before tcr-command:

  • This looks promising. It will work

Result:

  • Worked!

Nineteenth test run

Test:

it('returns "1, 2, Fizz" for "1,2,3"', () => {
    assert.equal(fizzBuzzer.string('1, 2, 3'), '1, 2, Fizz')
  })

Production code - no change:

const string = (numbers) => {
  return numbers
    .split(',')
    .map((n) => n.trim())
    .map((n) => single(n))
    .join(', ')
}

Feeling before tcr-command:

  • Confident and, again, pretty sure this is the final implementation

Result:

  • IT WORKED and this should be it.

Twenthiet test run

I now did a full test like this:

it('the complete kata', () => {
    assert.equal(fizzBuzzer.string('1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15'), '1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz, 11, Fizz, 13, 14, FizzBuzz')
})

Feeling before tcr-command:

  • VERY NERVOUS - because that took some time to write.

Result:

  • IT WORKED and this is now done

Summary

This was very interesting and educational to do. I was particularly happy to see how my reasoning changed during the exercise:

  • At first I was very nervous running the tests
  • Then I started to do smaller and smaller changes
  • In the end, I instead felt confident and I found myself thinking: Better commit this, by running the tests.

In the end, the revert and deletion of my code felt like a relief almost and since I didn’t write that much code I took the opportunity to think through what I needed to do once more.

All in all, I ended up with better code written in smaller chunks. That made me feel pretty good.

Hope you found this interesting to follow along in. My code is here

Published by Marcus Hammarberg on Last updated