Set up a class to store the game, the details of the pieces, a factory that places the initial pieces and a few tests around that as well.
Build some movement logic into the piece class
Check for walls
Make sure that I can't move a piece on top of another.
Start testing for valid jump locations.
Finished jump tests, decided I was being silly with the continue statements and refactored into normal if statements.
Ooops, regex replace left tests the wrong way around. Fixed that.
Check some of the simpler turn rules - piece must exist, piece must be the right colour.
Jump ahead to one of the more complicated rules to see if it's easily do-able.

It works, but it could be a little more elegant.