BDD/TDD projects

I was wondering if there were any BDD/TDD projects or tutorials that anyone could recommend?

I'm currently learning elixir and when I was learning rust, I really enjoyed a tutorial called pngme. It has test cases and a specification but left you to implement everything else. Link to pngme: https://picklenerd.github.io/pngme_book/introduction.html

Does anyone know of any similar projects but for elixir?

Thanks in advance