Pythonmonkeypatch.setattr() 在模块范围内带有 pytest 固定装置

Question

首先，我的项目目录的相关部分如下所示：

??? my_package
    ??? my_subpackage
    ?   ??? my_module.py
    |   ??? other_module.py
    ??? tests
        ??? my_subpackage
            ??? unit_test.py

我正在编写一些测试unit_test.py，需要在模块级别模拟外部资源。我想使用pytest fixture模块级范围并pytest monkeypatch完成此操作。这是我尝试过的片段unit_test.py：

import unittest.mock as mock
import pytest
from my_package.my_subpackage.my_module import MyClass


@pytest.fixture(scope='function')
def external_access(monkeypatch):
    external_access = mock.MagicMock()
    external_access.get_something = mock.MagicMock(
        return_value='Mock was used.')
    monkeypatch.setattr(
        'my_package.my_subpackage.my_module.ExternalAccess.get_something',
        external_access.get_something)


def test_get_something(external_access):
    instance = MyClass()
    instance.get_something()
    assert instance.data == 'Mock was used.'

一切正常。但是当我尝试将第 8 行从 更改@pytest.fixture(scope='function')为 时@pytest.fixture(scope='module')，出现以下错误。

ScopeMismatch: You tried to access the 'function' scoped fixture 'monkeypatch' with a 'module' scoped request object, involved factories
my_package\tests\unit_test.py:7:  def external_access(monkeypatch)
..\..\Anaconda3\envs\py37\lib\site-packages\_pytest\monkeypatch.py:20:  def monkeypatch()

有谁知道如何使用模块级范围进行monkeypatch？

如果有人想知道，这也是这两个模块的样子。

my_module.py

from my_package.my_subpackage.other_module import ExternalAccess


class MyClass(object):
    def __init__(self):
        self.external_access = ExternalAccess()
        self.data = None

    def get_something(self):
        self.data = self.external_access.get_something()

other_module.py

class ExternalAccess(object):
    def get_something(self):
        return 'Call to external resource.'

Answer 1

我发现了指导方式的这个问题。我需要对模块级范围的解决方案进行一些更改。unit_test.py现在看起来像这样：

import unittest.mock as mock

import pytest

from my_package.my_subpackage.my_module import MyClass


@pytest.fixture(scope='module')
def monkeymodule():
    from _pytest.monkeypatch import MonkeyPatch
    mpatch = MonkeyPatch()
    yield mpatch
    mpatch.undo()

@pytest.fixture(scope='module')
def external_access(monkeymodule):
    external_access = mock.MagicMock()
    external_access.get_something = mock.MagicMock(
        return_value='Mock was used.')
    monkeymodule.setattr(
        'my_package.my_subpackage.my_module.ExternalAccess.get_something',
        external_access.get_something)


def test_get_something(external_access):
    instance = MyClass()
    instance.get_something()
    assert instance.data == 'Mock was used.'

Answer 2

从 pytest 6.2 开始，这变得更加简单，这要归功于pytest.MonkeyPatch类和上下文管理器（https://docs.pytest.org/en/6.2.x/reference.html#pytest.MonkeyPatch）。根据 Rich 的答案，monkeymodule现在可以将装置编写如下：

@pytest.fixture(scope='module')
def monkeymodule():
    with pytest.MonkeyPatch.context() as mp:
        yield mp

@pytest.fixture(scope='function')
def external_access(monkeymodule):
    external_access = mock.MagicMock()
    external_access.get_something = mock.MagicMock(
        return_value='Mock was used.')
    monkeymodule.setattr(
        'my_package.my_subpackage.my_module.ExternalAccess.get_something',
        external_access.get_something)