Python-模拟嵌套的数据库调用

我正在尝试为下面的some\u func.py中的some\u func函数编写单元测试。我不想在测试期间连接到任何数据库，我想模拟对DB的任何调用

因为实际的db调用有点嵌套，所以我无法让它工作。在这种情况下，如何修补任何db交互

db_module.py

import MySQLdb

from random_module.config.config_loader import config
from random_module.passwd_util import get_creds

class MySQLConn:

    _conn = None

    def __init__(self):
        self._conn = self._get_rds_connection()

    def get_conn(self):
        return self._conn

    def _get_rds_connection(self):
        """
        Returns a conn object after establishing connection with the MySQL database

        :return: obj: conn
        """

        try:

            logger.info("Establishing connection with MySQL")

            username, password = get_creds(config['mysql_dev_creds'])

            connection = MySQLdb.connect(
                host=config['host'],
                user=username,
                passwd=password,
                db=config['db_name'],
                port=int(config['db_port']))

            connection.autocommit = True

        except Exception as err:
            logger.error("Unable to establish connection to MySQL")
            raise ConnectionAbortedError(err)

        if (connection):
            logger.info("Connection to MySQL successful")
            return connection
        else:
            return None

db_mysql = MySQLConn()

一些函数

from random_module.utils.db_module import db_mysql

def some_func():

    try: 

        db_conn = db_mysql.get_conn()
        db_cursor = db_conn.cursor()

        results = db_cursor.execute("SELECT * FROM some_table")
        results = db_cursor.fetchall()

        result_set = []

        for row in results:

            result_set.insert(i, row['x'])
            result_set.insert(i, row['y'])

    except Exception:
        logger.error("some error")

    return result_set

目录结构-

src
├──pkg
|   ├── common
|      |___ some_func.py
|      |___ __init__.py
|       
|   ├── utils
|      |___ db_module.py
|      |___ __init__.py
|
| __init__.py

---

您应该在

some_module.py

中模拟

db_mysql

，然后断言预期调用是在执行

some_func（）

之后进行的

from unittest TestCase
from unittest.mock import patch
from some_module import some_func

class SomeFuncTest(TestCase):

    @patch('some_module.db_mysql')
    def test_some_func(self, mock_db):
        result_set = some_func()

        mock_db.get_conn.assert_called_once_with()
        mock_cursor = mock_db.get_conn.return_value
        mock_cursor.assert_called_once_with()

        mock_cursor.execute.assert_called_once_with("SELECT * FROM some_table")
        mock_cursor.fetchall.return_value = [
            {'x': 'foo1', 'y': 'bar1'},
            {'x': 'foo2', 'y': 'bar2'}
        ]
        mock_cursor.fetchall.assert_called_once_with()

        self.assertEqual(result_set, ['foo1', 'bar1', 'foo2', 'bar2'])

---

您需要模拟这一行：

db\u conn=db\u mysql.get\u conn（）

get_conn方法的返回值是您感兴趣的

from random_module.utils.db_module import db_mysql

@mock.patch.object(db_mysql, 'get_conn')
def test_some_func(self, mock_get):
    mock_conn = mock.MagicMock()
    mock_get.return_value = mock_conn
    mock_cursor = mock.MagicMock()
    mock_conn.cursor.return_value = mock_cursor

    expect = ...
    result = some_func()

    self.assertEqual(expect, result)
    self.assertTrue(mock_cursor.execute.called)

---

正如您所看到的，设置这些模拟非常复杂。这是因为您正在实例化函数内部的对象。更好的方法是重构代码以注入游标，因为游标是唯一与此函数相关的东西。更好的方法是创建一个数据库夹具来测试函数是否与数据库正确交互

我编辑了这个问题，因为我有some_func.py模块和some_func方法。当我尝试修补时，我正在执行@mock.patch（'pkg.common.some_func.db_mysql'）。但这会导致AttributeError:“module”对象没有属性“some_func”。我甚至在公共目录中列出了init.py。在

pkg

和

common

中有一个更新了dir结构。我在每个文件夹中都有一个

\uuu init\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu？看来补丁不知怎么搞混了。不，我不知道。由于db_mysql正在另一个类中实例化，您认为这可能是罪魁祸首吗？