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模拟类：Mock（）或patch（）？

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问题：模拟类：Mock（）或patch（）？
回答 0
回答 1

问题：模拟类：Mock（）或patch（）？

我在Python中使用模拟，并想知道这两种方法中哪一种更好（请参阅：更多pythonic）。

方法一：只需创建一个模拟对象并使用它即可。代码如下：

def test_one (self):
    mock = Mock()
    mock.method.return_value = True 
    self.sut.something(mock) # This should called mock.method and checks the result. 
    self.assertTrue(mock.method.called)

方法二：使用补丁创建一个模拟。代码如下：

@patch("MyClass")
def test_two (self, mock):
    instance = mock.return_value
    instance.method.return_value = True
    self.sut.something(instance) # This should called mock.method and checks the result. 
    self.assertTrue(instance.method.called)

两种方法都做同样的事情。我不确定这些差异。

谁能启发我？

点击查看英文原文

I am using mock with Python and was wondering which of those two approaches is better (read: more pythonic).

Method one: Just create a mock object and use that. The code looks like:

def test_one (self):
    mock = Mock()
    mock.method.return_value = True 
    self.sut.something(mock) # This should called mock.method and checks the result. 
    self.assertTrue(mock.method.called)

Method two: Use patch to create a mock. The code looks like:

@patch("MyClass")
def test_two (self, mock):
    instance = mock.return_value
    instance.method.return_value = True
    self.sut.something(instance) # This should called mock.method and checks the result. 
    self.assertTrue(instance.method.called)

Both methods do the same thing. I am unsure of the differences.

Could anyone enlighten me?

回答 0

mock.patch与…是一个非常不同的生物mock.Mock。 patch 用模拟对象替换该类，并允许您使用模拟实例。看一下这个片段：

>>> class MyClass(object):
...   def __init__(self):
...     print 'Created MyClass@{0}'.format(id(self))
... 
>>> def create_instance():
...   return MyClass()
... 
>>> x = create_instance()
Created MyClass@4299548304
>>> 
>>> @mock.patch('__main__.MyClass')
... def create_instance2(MyClass):
...   MyClass.return_value = 'foo'
...   return create_instance()
... 
>>> i = create_instance2()
>>> i
'foo'
>>> def create_instance():
...   print MyClass
...   return MyClass()
...
>>> create_instance2()
<mock.Mock object at 0x100505d90>
'foo'
>>> create_instance()
<class '__main__.MyClass'>
Created MyClass@4300234128
<__main__.MyClass object at 0x100505d90>

patchMyClass以允许您控制所调用函数中类的用法的方式进行替换。修补类后，对该类的引用将完全由模拟实例替换。

mock.patch通常在测试要在测试内部创建类的新实例的东西时使用。 mock.Mock实例更清晰，更可取。如果您的self.sut.something方法创建了的实例MyClass而不是将实例作为参数接收，则mock.patch此处适当。

点击查看英文原文

mock.patch is a very very different critter than mock.Mock. patch replaces the class with a mock object and lets you work with the mock instance. Take a look at this snippet:

>>> class MyClass(object):
...   def __init__(self):
...     print 'Created MyClass@{0}'.format(id(self))
... 
>>> def create_instance():
...   return MyClass()
... 
>>> x = create_instance()
Created MyClass@4299548304
>>> 
>>> @mock.patch('__main__.MyClass')
... def create_instance2(MyClass):
...   MyClass.return_value = 'foo'
...   return create_instance()
... 
>>> i = create_instance2()
>>> i
'foo'
>>> def create_instance():
...   print MyClass
...   return MyClass()
...
>>> create_instance2()
<mock.Mock object at 0x100505d90>
'foo'
>>> create_instance()
<class '__main__.MyClass'>
Created MyClass@4300234128
<__main__.MyClass object at 0x100505d90>

patch replaces MyClass in a way that allows you to control the usage of the class in functions that you call. Once you patch a class, references to the class are completely replaced by the mock instance.

mock.patch is usually used when you are testing something that creates a new instance of a class inside of the test. mock.Mock instances are clearer and are preferred. If your self.sut.something method created an instance of MyClass instead of receiving an instance as a parameter, then mock.patch would be appropriate here.

回答 1

我有一个YouTube视频。

简短答案：mock在传递要嘲笑的东西时使用，patch如果不是，则使用。在这两种方法中，mock是首选，因为它意味着您正在使用适当的依赖注入来编写代码。

愚蠢的例子：

# Use a mock to test this.
my_custom_tweeter(twitter_api, sentence):
    sentence.replace('cks','x')   # We're cool and hip.
    twitter_api.send(sentence)

# Use a patch to mock out twitter_api. You have to patch the Twitter() module/class 
# and have it return a mock. Much uglier, but sometimes necessary.
my_badly_written_tweeter(sentence):
    twitter_api = Twitter(user="XXX", password="YYY")
    sentence.replace('cks','x') 
    twitter_api.send(sentence)
点击查看英文原文

I’ve got a YouTube video on this.

Short answer: Use mock when you’re passing in the thing that you want mocked, and patch if you’re not. Of the two, mock is strongly preferred because it means you’re writing code with proper dependency injection.

Silly example:

# Use a mock to test this.
my_custom_tweeter(twitter_api, sentence):
    sentence.replace('cks','x')   # We're cool and hip.
    twitter_api.send(sentence)

# Use a patch to mock out twitter_api. You have to patch the Twitter() module/class 
# and have it return a mock. Much uglier, but sometimes necessary.
my_badly_written_tweeter(sentence):
    twitter_api = Twitter(user="XXX", password="YYY")
    sentence.replace('cks','x') 
    twitter_api.send(sentence)