提问人：Aditya Bangard 提问时间：11/4/2023 更新时间：11/13/2023 访问量：43
mock.patch 在 with 语句范围之外泄漏模拟对象
mock.patch leaks mocked object outside the scope of with statement
问：
我在文件夹控制器下有以下三个python文件
- math.py
class Math:
def __init__(self, a, b):
self.a = a
self.b = b
def addition(self):
return self.a + self.b
- calculation.py
from controller.math import Math
def perform_addition():
math = Math(1, 2)
return math.addition()
- test_sample.py
from unittest.mock import MagicMock, patch
def test_addition():
mock_math = MagicMock()
with patch('controller.math.Math', return_value=mock_math) as MockClass:
instance = MockClass.return_value
instance.addition.return_value = 100
from controller.calculation import perform_addition
output = perform_addition()
print(output) # prints 100
post_patch_output = perform_addition()
print(post_patch_output) # prints 100 but expected 3
当我执行test_addition时，我希望返回 3，但它返回 100，即模拟输出。我很好奇我在这里错过了什么？post_patch_output
从这里的 mock.patch 文档来看，它说的情况看起来不像这里的情况When the function/with statement exits the patch is undone.
答：
0赞
frankfalse
11/9/2023
#1
对函数的更正test_addition
您必须修改文件，如下所示：test_sample.py
from unittest.mock import MagicMock, patch
from controller.calculation import perform_addition
def test_addition():
mock_math = MagicMock()
#with patch('controller.math.Math', return_value=mock_math) as MockClass:
with patch('controller.calculation.Math', return_value=mock_math) as MockClass:
instance = MockClass.return_value
instance.addition.return_value = 100
#from controller.calculation import perform_addition
output = perform_addition()
print(output) # prints 100
post_patch_output = perform_addition()
print(post_patch_output) # prints 100 but expected 3
test_addition()
这是执行的输出：test_addition()
100
3
如你所料。
代码中的错误
- 您必须在文件内而不是在 .如果修补所有指向 Mock 对象的引用。因此，每次调用它时，都会使用 Mock 对象，而不是真正的类
Mathcalculation.pymath.pycontroller.math.MathMathperform_addition()Math - 前面的修改就足够了，但我更喜欢在文件顶部执行导入，而不是在方法内部执行导入
from controller.calculation import perform_additiontest_addition - 请记住，当您执行（即使在上下文管理器中）时，导入的名称（在您的情况下）在脚本中可用并引用对象。
importperform_addition
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