Python：对象属性上的模拟side_effect

Question

是否有可能对属性有side_effect？如果我看看Mock文档，它似乎只能在对象方法上使用。

我试图测试以下：

def get_object(self): 
    try: 
     return self.request.user.shop 
    except Shop.DoesNotExist: 
     return None 

我想店提出一个DoesNotExist例外。

猜测也许我不够清楚，但我正在谈论的空洞模拟库。

http://www.voidspace.org.uk/python/mock/index.html

Answer 1

笔者做了一个博客帖子这个问题。我去了，看起来像这样第一个解决方案：

class UserMock(Mock): 
    @property 
    def shop(self): 
     raise Shop.DoesNotExist() 

http://www.voidspace.org.uk/python/weblog/arch_d7_2010_11_20.shtml#e1196

Answer 2

是的，你可以使用属性吧：

In [1]: class ShopDoesNotExist(Exception): 
    ...:  pass 
    ...: 

In [2]: class User(object): 
    ...:  @property 
    ...:  def shop(self): 
    ...:   raise ShopDoesNotExist 
    ...: 
    ...: 

In [3]: u = User() 

In [4]: u.shop 
--------------------------------------------------------------------------- 
ShopDoesNotExist       Traceback (most recent call last) 

Answer 3

值得一提的是，现在存在PropertyMock类：

>>> m = MagicMock() 
>>> p = PropertyMock(side_effect=ValueError) 
>>> type(m).foo = p 
>>> m.foo 
Traceback (most recent call last): 
.... 
ValueError 

这例子是taken from the official site。

Answer 4

您也可以尝试使用PropertyMock作为new_callable参数来修补相关字段。

实施例：

from unittest import TestCase 
import mock 
from django import models 
from django.core.exceptions import ObjectDoesNotExist 

class Foo(models.Model): 
    # ... 
    @property 
    def has_pending_related(self): 
     try: 
      return self.related_field.is_pending 
     except ObjectDoesNotExist: 
      return False 

class FooTestCase(TestCase): 
    # ... 
    @mock.patch.object(Foo, 'related_field', new_callable=mock.PropertyMock) 
    def test_pending_related(self, related_field): 
     related_field.side_effect = ObjectDoesNotExist 
     foo = Foo() 
     self.assertFalse(foo.has_pending_related)