Found a nice video of someone implementing Tic Tac Toe in Clojure, complete with an AI opponent.
I learned quite a bit watching it. Enjoy!
Looks good 
Added it to my “watch this later” list.
There is also similar one in haskell by the same author: TicTacToe In Haskell Using TDD (Advanced) - YouTube
And some comments to katas: Using Katas To Improve | 8th Light
8th light blogs inspired me to do programming katas regularly.