def test_str3(self):
date = datetime(2017, 6, 4)
item = TodoItem('implement TodoItem class', date)
item.mark()
test_string = item.__str__()
self.assertEqual(test_string[1], 'x', 'Wrong sign')
def test_unmark(self):
date = datetime(2017, 6, 4)
item = TodoItem('implement TodoItem class', date)
item.mark()
item.unmark()
self.assertEqual(item.is_done, False, 'Item wasn\'t unmarked')