def test_add_undo(self):
grid = Grid(5)
grid.add_black_cell(1, 2)
self.assertEqual(True, grid.is_black_cell(1, 2))
self.assertEqual(True, grid.is_black_cell(5, 4))
self.assertEqual([(1, 2)], grid.undo_stack)
self.assertEqual([], grid.redo_stack)
grid.undo()
self.assertEqual(False, grid.is_black_cell(1, 2))
self.assertEqual(False, grid.is_black_cell(5, 4))
self.assertEqual([], grid.undo_stack)
self.assertEqual([(1, 2)], grid.redo_stack)
def test_undo_with_empty_stack(self):
grid = Grid(5)
grid.undo()
self.assertListEqual([], grid.undo_stack)
self.assertListEqual([], grid.redo_stack)
pass
