In a few cases, the board resets randomly to a pseudo-random position when playing the game. This issue is more prominent in the AI vs AI game mode.

The FEN k7/6p1/8/q4P1K/8/8/8/8 b KQkq - 0 1, and similar FENs with the same arrangement of the King, Queen and the pawns, allow the King to be captured due to a bug in validation of the En-passant move.

The board arrangement can be reproduced by uncommenting Line 5 in defs/Constants.py and commenting Line 4 in the same file.

The tests fail at a depth of 5.

Logs are below:

self = <move_test.Tests testMethod=test_fifth>

    def test_fifth(self) -> None:
        gs = board.GameState()
>       self.assertEqual(self.total_moves(5, gs), 4865609)
E       AssertionError: 4865351 != 4865609

move_test.py:44: AssertionError