def test_pfd_clear_column_3(self):
matrix = [[3, 0, 0, 0], [1, 0, 1, 0], [1, 1, 0, 0], [2, 0, 1, 1]]
pfd_clear_column(matrix, 2)
self.assert_(matrix == [[3, 0, 0, 0], [0, 0, 1, 0], [1, 1, 0, 0], [1, 0, 1, 1]])
def test_pfd_clear_column_2(self):
matrix = [[1, 0], [1, 1]]
pfd_clear_column(matrix, 1)
self.assert_(matrix == [[1, 0], [0, 1]])