class Mysql:    @classmethod    def connect(cls):        mysql_info = {            "host": "litemall.hogwarts.ceshiren.com",            "port": 13306,            "user": "test",            "password": "test123456",            "database": "litemall",            "charset": "utf8mb4"        }        conn = pymysql.Connect(**mysql_info)        return conn
    @classmethod    def execute(cls, sql):        cnn = cls.connect()        sor = cnn.cursor()        sor.execute(sql)        res = sor.fetchall()        sor.close()        cnn.close()        return res

    def test_cart_add(self, good_sn='CC102101'):        """测试添加购物车功能"""        with allure.step("获取商品的id"):            ids = self.good.id(good_sn)        with allure.step("获取商品的good_id和product_id"):            good_id = ids[0]            product_id = ids[1]        sql = f"""                         SELECT number FROM litemall_cart where goods_sn='{good_sn}' and goods_id='{good_id}'        """        good_num1 = Mysql.execute(sql)[0][0]        print(good_num1)        with allure.step("添加商品到购物车"):            print(self.cart.add(good_id, product_id))        good_num2 = Mysql.execute(sql)[0][0]        print(good_num2)        assert good_num2 - good_num1 == 1