def test_change_by(self):
        k = 'more'
        self.assertEqual(3, self.Counter.change_by(k, 3))       # increase 0 by 3
        self.assertEqual(3 - 1, self.Counter.change_by(k, -1))  # decrease 3 by 1
dataset/ETHPy150Open tevino/mongu/tests/test_counter.py/CounterTests.test_change_by/original