Have you ever written a unit test and it seems to take a long time to make green?

The diamond pattern kata on Codewars might make you fall into that position again.

The workshop at Agile Scotland conf by Seb Rose motivated me to write this post.

Test-driven development requires you to write a test first which helps you to move a step closer to solving the problem. A classic workflow is Red, Green, Refactor. That means write a failing unit test first (red), make it pass (green) and anything that can be done to improve the code quality (refactor). More on classic TDD read The cycles of TDD by Uncle Bob.

Each test passing should give you confidence to commit to master and the pace should be consistent. So there should not be a sudden slow down in your progress. I will explain more after the first round below.

First round

Be strict and spend 20 minutes trying to solve the diamond pattern kata using classic TDD.

** Start now and come back here in 20 minutes**

No problem if you have not solved it. What you need to do is be aware of where you got stuck. Are you stuck about two or four unit tests in? Is it testing pattern(2)?

pattern(2) ->

Why (╯°□°)╯︵ ┻━┻ …

Why is this the test that is stopping you?

Well you might have noticed you are solving the whole of the kata at this point. This is quite complex for our minds to handle all the cases to resolve. We struggle where to start but too many test cases overwhelm our thoughts.

How to make progress?

First brain storm all cases you need to handle to help reduce the overload. Below are case you need to cover:

  • Spacing for each row
  • Increment number to row number and then decrement to one to reflect the numbers e.g. 12321
  • Add new line at end of each row
  • Reflex the top half of the diamond

Recycling your test

Idea is to take each of these points one at a time and start where you got stuck. Each time you solve one update the assert to handle the next point. Don’t make another assert as the previous one will break. Essentially progress by tweaking the test until it gets to the point it is useful for regression.

Notable the workflow pattern is different as you will be on the same unit test. It will be something like red, green, green, green, … until you solve it.

Second round

Try again and spend 20 minutes trying to solve the diamond pattern kata using this recycling method.

After the 20 minutes there should be a better feeling of progress instead of overwhelmed and blocked.


I found this a useful approach for solving complex problems in unit tests. Remove that nagging worry writing a complete function break the problem down into manageable chunks and this will help provide confident progression.

Has this helped you solve the kata? Please write comments below on what you think of this approach below.