def test_add(self):
board = Board()
self.assertTrue(all(square == None for square in board.squares()))
board.add(Color.white, Pawn, Position(3, 4))
board.add(Color.black, Pawn, Position(6, 6))
self.assertEqual(Color.white, board.at(Position(3, 4)).color)
self.assertEqual(Pawn, type(board.at(Position(3, 4))))
self.assertEqual(Color.black, board.at(Position(6, 6)).color)
self.assertEqual(Pawn, type(board.at(Position(6, 6))))
self.assertEqual(2, len(list(board.pieces())))
for position in board.positions():
if position not in (Position(3, 4), Position(6, 6)):
self.assertIsNone(board.at(position))
