python+selenium+unnitest写一个完整的登陆的验证

import unittest
from selenium import webdriver
from time import sleep

class lonInTest (unittest.TestCase):
    @classmethod
    def setUp(self):
        self.driver = webdriver.Firefox()
        self.driver.implicitly_wait(30)
    def test_login_sucess(self):
         self.login("XXXXX","XXXXXXX")
         sleep(3)
         logoutName = self.driver.find_element_by_class_name("menu-link-label")
         self.assertTrue('修改密码' in logoutName.text)

    def login(self, username, password):
        self.driver.get("http:XXXXXXXXXX")
        input_field = self.driver.find_element_by_name("username")
        input_field.clear()
        input_field.send_keys(username)

        input_password = self.driver.find_element_by_name("password")
        input_password.clear()
        input_password.send_keys(password)

        login = self.driver.find_element_by_tag_name("button")
        login.click()

    def tearDown(self):
        self.driver.quit()

unittest.main()

作为一个刚开学习python+selenium+unnitest的小白人员，说一下我写这段代码遇到的问题吧

问题：运行程序就报TypeError: test_login() missing 2 required positional arguments: 'username' and 'password'

后来经过种种排查发现：login函数之前的test去掉就可以了，因为login是内部调用的函数，test开头的是每一条用例

def test_login_sucess(self):
self.test_login("XXXXXX","XXXXXX")
sleep(3)
logoutName = self.driver.find_element_by_class_name("menu-link-label")
self.assertTrue('修改密码' in logoutName.text)

def test_login(self, username, password):
self.driver.get("XXXXXXXXXXXXX")
input_field = self.driver.find_element_by_name("username")
input_field.clear()
input_field.send_keys(username)