Update decorators to take an optional 'piece' argument. Attributes are set on the piece, rather than being passed to the test raw.
Update decorators to pass keyword arguments named for the type of piece they pass.
Update Rook tests to take advantage of tweaked decorators.
Mend decorators for proper argument taking. Update rook tests to take advantage of decorators.
Update docstring for decorators.
Fix all_players docstring.
Remove print statement from Rook test.
Update Knight tests to take advantage of decorators.
Add test for empty board to Knight suite.
Add imports and empty board actual_cache test methods to the Queen and King test suites.
Mend docstring for all_piece_types decorator.
Add test decorator for pieces with has_moved attribute.
Update Pawn test suite to make use of test decorators.