模拟对象的构造函数仍然被调用？

Question

我对 Python 和单元测试真的很陌生，我现在正在尝试为处理程序编写单元测试。

处理程序的简化版本如下所示：

some_handler.py

def handleEvent(event): 
   user = event....
   action = event...
   response = getIsAuthorized(user, action)
   return convertToHttpResponse(response)

getIsAuthorized(user, action):
   ...
   authorizer = SomeAuthorizer()
   return authorizer.isAuthorized(user, action)

SomeAuthorizer 是一个简单的类：

some_authorizer.py

class SomeAuthorizer(object):
   __init__(self):
      # some instantiation of stuff needed for the 3P client
      ... 
      # creation of some 3P auth client
      self.client = Some3PClient(...)

   is_authorized(user, action): 
      return self.client.is_authorized(user, action)

代码本身按预期工作，但我的测试让我很痛苦。 我让它在某些情况下工作：

    @patch.object(SomeAuthorizer, 'is_authorized')
    def test_authorization_request_not_authorized(self, mock_is_authorized):
        mock_is_authorized.return_value = False
          
        response = handle_request(test_event("test_user", "testing"))
        assert response == status_code(200, False)

但是当另一个开发人员在他们的机器上运行测试时，它失败了，原因似乎是因为他们没有在本地设置 Authorizer 的构造函数所需的一些环境内容（他们在本地得到的错误是在测试运行时创建 SomeAuthorizer 实例的问题）。但我的理解是，构造函数甚至不应该被调用，因为它被嘲笑了？不是这样吗？

关于如何解决这个问题的任何提示？我一直在拼命想了解模拟是如何工作的，以及补丁/模拟的组合会起作用，但它不会走得太远。

Answer 1

这是您可能希望用作参考的有效解决方案。这将模拟整个 SomeAuthorizer 类，因此它的 __init__() 不会被执行，也不会像 is_authorized() 这样的任何方法被执行。

文件树

$ tree
.
├── some_authorizer.py
├── some_handler.py
└── test_auth.py

some_authorizer.py

class Some3PClient:
    def is_authorized(self, user, action):
        return True  # Real implementation returns True


class SomeAuthorizer(object):
   def __init__(self):
      print("Real class __init__ called")
      self.client = Some3PClient()

   def is_authorized(self, user, action):
      print("Real class is_authorized called")
      return self.client.is_authorized(user, action)

some_handler.py

from some_authorizer import SomeAuthorizer  # The module we want to mock. To emphasize, the version we need to mock is "some_handler.SomeAuthorizer" and not "some_authorizer.SomeAuthorizer".


def handleEvent(event):
   user = "event...."
   action = "event..."
   response = getIsAuthorized(user, action)
   return convertToHttpResponse(response)


def getIsAuthorized(user, action):
   authorizer = SomeAuthorizer()
   return authorizer.is_authorized(user, action)


def convertToHttpResponse(response):
    return (200, response)

test_auth.py

from unittest.mock import patch

from some_handler import handleEvent


def test_real_class():
    response = handleEvent("test_event")
    assert response == (200, True)
    print(response)


@patch("some_handler.SomeAuthorizer")  # As commented in some_handler.py, patch the full path "some_handler.SomeAuthorizer" and not "SomeAuthorizer" nor "some_authorizer.SomeAuthorizer". If you want to patch the latter for all that uses it, you have to reload the modules that imports it.
def test_mock_class(mock_some_authorizer):
    mock_some_authorizer.return_value.is_authorized.return_value = False  # Mock implementation returns False

    response = handleEvent("test_event")
    assert response == (200, False)
    print(response)

输出

$ pytest -q -rP
============================================================================================ PASSES ============================================================================================
_______________________________________________________________________________________ test_real_class ________________________________________________________________________________________
------------------------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------------------------
Real class __init__ called
Real class is_authorized called
(200, True)
_______________________________________________________________________________________ test_mock_class ________________________________________________________________________________________
------------------------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------------------------
(200, False)
2 passed in 0.05s