def test_compress(self):
board = Board(4, 4)
start = [2, 0, 4, 0]
end_backward = [2, 4, 0, 0]
end_forward = [0, 0, 2, 4]
self.assertEqual(end_backward, board._Board__compress(start, 'left'))
self.assertEqual(end_forward, board._Board__compress(start, 'right'))
self.assertEqual(end_backward, board._Board__compress(start, 'up'))
self.assertEqual(end_forward, board._Board__compress(start, 'down'))
