Original Kata: https://github.com/emilybache/Tennis-Refactoring-Kata
This Kata actually consists of three sub-katas: TennisGame1, TennisGame2 and TennisGame3.
Each one is a different implementation of the problem, but the behaviour is the same.
I have refactored TennisGame1 and started working on TennisGame2, but may not finish now.
Maybe I'll come back to it in the future.