引数のテストをするには？

check_argv.py

# -*- coding:utf-8 -*-
# こんな感じで書くよーと教えてもらいました

import sys
import unittest
from StringIO import StringIO
from url_checker import *


class TestCaseForArgparse(unittest.TestCase):
    def test_options_judgment(self):
        # set STDERR to null
        _stderr = sys.stderr
        sys.stderr = StringIO()

        sys.argv = ['script_name', '-a']  # set arguments
        self.assertRaises(SystemExit, options_judgment)

        sys.argv = []  # clear
        sys.stderr = _stderr  # restore STDERR


if __name__ == '__main__':
    unittest.main()