如何使用pytest-mock或magicmock模拟导入的对象 [英] How to mock a imported object with pytest-mock or magicmock

问题描述

我试图了解mock/monkeypatch/pytest-mock功能.

让我知道是否可行.如果不能，请建议我如何测试此代码.

Let me know if this is possible. If not could you please suggest how I can test this code.

我的代码结构:

/
./app
../__init__.py
../some_module1
.../__init__.py
../some_module2
.../__init__.py
./tests
../test_db.py

/app/__init__.py是启动我的应用程序(如果有帮助的话，是Flask应用程序)的地方，同时还初始化了到MongoDB数据库的数据库连接对象:

The /app/__init__.py is where my application (a Flask application if it helps) is started along with initializing a database connection object to a MongoDB database:

# ...

def create_app():
  # ...
  return app

db_conn = DB()

some_module1和some_module导入db_conn对象并将其用作其功能的一部分:

The some_module1 and some_module import the db_conn object and use it as part of their functions:

## some_module1/__init__.py
from app import db_conn

...
db = db_conn.db_name2.db_collection2

def some_func1():
    data = db.find()
    # check and do something with data
    return boolean_result

...

## some_module2/__init__.py
from app import db_conn

...
db = db_conn.db_name1.db_collection1

def some_func2():
    data = db.find()
    # check and do something with data
    return boolean_result
...

在测试中，我想根据从数据库接收到的数据来测试我的代码是否正常运行. 我想模拟数据库，更具体地说是db_conn对象，因为我不想使用真实的数据库(设置和维护环境需要大量工作).

In my tests, I want to test if my code works properly based on the data received from the database. I want to mock the database, more specifically the db_conn object since I don't want to use a real database (which would be a lot of work setting up the environment and maintaining it).

关于如何模拟db_conn的任何建议?

Any suggestions on how I can emulate the db_conn?

我一直在探索pytest-mock和magicmock，但是我不认为或不知道如何在测试中模拟db_conn.

I've been exploring pytest-mock and magicmock but I don't think or know how to mock the db_conn in my test.

推荐答案

我相信您不对真实数据库中的案例进行测试是正确的，因为如果您使用外部依赖项，则不再进行单元测试.

I believe you are right not testing cases on a real database because it's not unit testing anymore if you are using external dependencies.

有可能指定return-value 并对其进行自定义(对于Mock或MagicMock对象，每次迭代甚至返回不同的返回值).

There is a possibility to specify return-value and customize it (different return values on each iteration even) for Mock or MagicMock objects.

from unittest.mock import Mock, patch 

from app import db_conn


@patch('app.db_conn.find')
def test_some_func1(db_con_mock):
    ...
    assert ...

请记住，在每个patch中，您都应指定db_conn的导入路径-使用db_conn **的路径(我假设每个测试中的路径都不相同) )，而不是它的定义位置.

Keep in mind that in each patch you should specify the import path of db_conn - the path where db_conn **is used (I assume it's a different path in each test), not where it is defined.

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