Refactor pamametrizing tests

[Sung-Kyu Yoo]

Removing duplicated test codes. See https://docs.pytest.org/en/6.2.x/parametrize.html

[Sung-Kyu Yoo]

ToDo List

• blockkit_test : #155
• client_test : #159
• command_test : #161
• models_test
• utils_test