def test_should_choose_move_worst_positioned_tile():
tiles = [1, 8, 2, 4, None, 3, 7, 6, 5]
solver = Solver(tiles)
possibilities = solver.lookahead(tiles)
move_scores = solver.prioritize(possibilities)
move_priorities = sorted(move_scores, key=move_scores.get)
assert move_priorities[0] == 8
def test_can_provide_lookahead():
puzzle = Solver([1, None, 3, 2])
assert puzzle.lookahead([1, None, 3, 2]) == {
1: [None, 1, 3, 2],
2: [1, 2, 3, None]
}