This kata is from https://github.com/qmates-tech/openchat-kata
The original idea of the kata is from Robert C. Martin and Sandro Mancuso in "London vs. Chicago" cleancoders serie.
You can use the main branch to start doing this kata.
As Uncle Bob and Sandro Mancuso did, my goal was to dive into these two approaches of TDD.
In "inside-out" and "outside-in" branches you can find what are, imho, the first steps following that aproach. I hardly invite you to try both before to see my code.