Kata: Scrabble sets in Clojure

I recently did the Scrabble sets kata in Clojure.

I used a mix of a bit of TDD, a lot of REPL-driven development (RDD) following this cycle:

1. Write a failing test (using examples that a bit more complicated than the typical ones you use when doing only TDD).
2. Explore and triangulate on the REPL until I made the test pass with some ugly but complete solution.
3. Refactor the code to make it more readable.

I'm founding that this way of working in Clojure is very productive for me.

These are the tests I wrote using Midje:

and this the resulting code:

See all the commits here if you want to follow the process.

You can find all the code on GitHub.