def test_clone_detaches_future_writes(self):
board = Board()
board2 = board.clone()
board.o(0, 2)
self.assertTrue(board2.is_free(0, 2))
def test_clone_copies_already_set_cells(self):
board = Board()
board.o(0, 2)
self.assertFalse(board.clone().is_free(0, 2))