我正在尝试为我正在创建的电影网站编写一个测试用例。我想测试add_user方法。每次我从测试方法调用add_user()时，它都会在SQLite数据库中创建一个用户，然后作为失败返回该用户已经存在。

def add_user(self, name):
    param = {'name': name}
    query = text('Insert into users (name) values (:name)')
    check_usr_query = text('Select name from users '
                           'Where name = :name')

    check_usr = self._execute_query(check_usr_query, param).fetchone()

    if check_usr is not None:
       return 'User Already Exists in Database'
    else:
        with self.engine.connect() as conn:
            conn.execute(query, param)
            conn.commit()
        return 'Successfully added user'

import pytest
from DataManager.sql_data_manager import SQLiteDataManager

dataManager = SQLiteDataManager('DataManager/movie.db')

def test_add_user():
    name = 'Esth'
    test_data = dataManager.add_user(name)
    check_usr = dataManager.get_user_by_name(name)
    if test_data == 'Successfully added user':
        assert test_data == 'Successfully added user'
        print(name + ' added to db')
    elif test_data == 'User Already Exists in Database':
        assert check_usr is not None
        print(name + ' Already exists in the db')