如何在使用 mark.parametrize 装饰器的同时使用 patch 装饰器？

Question

我有一个测试功能可以修补一些东西。一旦我达到了超过 2 或 3 个补丁，该功能就开始看起来很糟糕

def test_bla():
    with patch(...):
        with patch(...):
            with patch(...):
                # test

所以我尝试开始使用装饰器。这是我的示例测试，当我引入补丁装饰器时，该测试会中断

import pytest
from unittest.mock import patch

class Example:
    def _run(self, x):
        return x

    def run(self, x):
        return self._run(x) + 1


@pytest.mark.parametrize('x', [1])
def test_example(x):
    assert Example().run(x) == 2


@pytest.mark.parametrize('x', [1])
@patch('Example._run', return_value=0)
def test_example_failure(x):
    with pytest.raises(AssertionError):
        assert Example().run(x) == 2

这是我得到的错误：

platform linux -- Python 3.6.13, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: ..., configfile: pytest.ini
plugins: metadata-1.11.0
collected 0 items / 1 error                                                                                                                                                                                    

==================================================================================================== ERRORS ====================================================================================================
________________________________________________________________________________________ ERROR collecting test_patch.py ________________________________________________________________________________________
In test_example_failure: function uses no argument 'x'
=========================================================================================== short test summary info ============================================================================================
ERROR test_patch.py
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
=============================================================================================== 1 error in 0.12s ===============================================================================================

我尝试更改装饰器顺序（正如我在一些答案中看到的那样）但这没有帮助。

---

我刚刚意识到的另一件事是，拥有一个没有参数化的测试参数是可行的！（我调整了一些代码，因为事实证明我无法从我自己的模块中修补类）

import pytest                                                                                                                                                                                                   
import random                                                                                                                                                                                                   
from unittest.mock import patch                                                                                                                                                                                 
                                                                                                                                                                                                                
class Example:                                                                                                                                                                                                  
    def _run(self, x):                                                                                                                                                                                          
        return random.randint(0, 6)                                                                                                                                                                             
                                                                                                                                                                                                                
    def run(self, x):                                                                                                                                                                                           
        return self._run(x) + 1                                                                                                                                                                                 
                                                                                                                                                                                                                
                                                                                                                                                                                                                
@pytest.mark.parametrize('x', [1])                                                                                                                                                                              
def test_example(x):                                                                                                                                                                                            
    assert Example().run(x) < 7                                                                                                                                                                                 
                                                                                                                                                                                                                
                                                                                                                                                                                                                
# @pytest.mark.parametrize('x', [1])                                                                                                                                                                            
@patch('random.randint', return_value=0)                                                                                                                                                                        
def test_example_failure(x):                # <<< How the heck does this work? 'x' is not defined!!                                                                                                                                                                   
    with pytest.raises(AssertionError):                                                                                                                                                                         
        assert Example().run(x) == 2    

Answer 1

@patch正在向测试MagicMock对象发送一个参数。如果您想发送另一个参数，@pytest.mark.parametrize您需要向测试添加另一个参数

@pytest.mark.parametrize('x', [1])
@patch('Example._run', return_value=0)
def test_example_failure(mocked_class, x):
    with pytest.raises(AssertionError):
        assert Example().run(x) == 2

# randint = <MagicMock name='randint' id='2158546057008'>
# x = 1