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:

mkdir fizzbuzz-tcr && cd fizzbuzz-tcr to create the directory and jump into it npm init -y to create an empty package.json file npm i -D mocha chai standard to install the tools I need touch index.js index.test.js to setup the two files we will work in I wrote scripts for test, lint and pretest "scripts" : { "lint" : "standard" , "pretest" : "standard" , "test" : "mocha -D bdd -R list ." } I’m linting my code with standard js The testing is done using mocha And the pretest script is automatically running the linting before the tests are executed 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 ) }) }) By running npm t i linted and ran the first test I created a .gitignore from the excellent https://www.gitignore.io/ 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

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