def test_of_2_queens(self):
     self.assertEqual(
         solveNQueens(2),
         [])
 def test_of_4_queens(self):
     self.assertEqual(
         solveNQueens(4),
         [['..Q.', 'Q...', '...Q', '.Q..'],
         ['.Q..', '...Q', 'Q...', '..Q.']])