python runtime_error ai_generated true

AttributeError: <module 'app.services.user'> does not have the attribute 'send_email'

ID: python/pytest-mock-patch-wrong-target

Also available as: JSON · Markdown · 中文
80%Fix Rate
90%Confidence
0Evidence
2024-04-03First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.10 active — — —
3.12 active — — —

Root Cause

`patch('app.services.user.send_email')` fails when the name is imported into the module under test from elsewhere. Patch must target the name *where it is looked up* (the consumer module), not where it is defined.

generic

中文

当被测模块通过 `from x import send_email` 导入名称时，`patch('app.services.user.send_email')` 会失败。patch 必须指向名称被查找的位置（使用方模块），而不是定义它的位置。

Workarounds

  1. 95% success 
    Patch where the name is used:

from unittest.mock import patch

@patch('app.services.user.send_email')
def test_signup(mock_send):
    ...
  2. 85% success 
    Change the import in the production module to a module-level reference and patch the module:

# app/services/user.py
from app import notifications
notifications.send_email(...)

# test
patch('app.services.user.notifications.send_email')

Dead Ends

Common approaches that don't work:

  1. 80% fail

    The module under test already bound the name at import time; patching the definition site does not affect the bound reference.

  2. 75% fail

    Creates a fake attribute on the module, but the code under test still calls the original binding, so the mock is never invoked.