[英]How to override (not patch) a single method in a python unit test
I've searched for hours. 我已经搜索了几个小时。 Can't find anyone even trying to do this. 甚至找不到试图这样做的人。 Hmmm. 嗯
I believe I have to override a single method within a class instance. 我相信我必须重写类实例中的单个方法。 I do not mean patch(return_value=)
. 我不是说patch(return_value=)
。 I need to make the method in question do something involving self
. 我需要使所讨论的方法做一些涉及self
事情。
I'll try to break it down. 我会尽力分解。 Liberally paraphrasing and including one of the many things I tried, which doesn't work ... 随意地改写并包括我尝试过的许多方法之一,这是行不通的...
class SetupClass(object):
def set_some_stuff(self):
data_list = functon_cannot_be_run_on_test_platform()
self.something = data_list[0]
self.something_else = data_list[1]
class UUT(object):
self.config = SetupClass()
assert self.config.something == 'foo'
class UnitTests(TestCase):
@patch('SetupClass')
def test_UUT(self, mock1):
def WedgeClass(SetupClass):
def set_some_stuff(self):
self.something = 'foo'
pass # I'm a Python newbie, in too deep
wedge_class = WedgeClass()
mock1.return_value = wedge_class # doesn't work. context errors
uut = UUT() # <-- would crash here, because assert above
Assume that I cannot make changes to UUT
or SetupClass
. 假设我无法对UUT
或SetupClass
进行更改。
Testing cannot even get off the ground because the assertion will fail, due to, SetupClass.functon_cannot_be_run_on_test_platform()
. 测试甚至无法启动,因为断言将由于SetupClass.functon_cannot_be_run_on_test_platform()
而失败。 Note that simply mocking SetupClass.functon_cannot_be_run_on_test_platform
will not solve the problem, because reasons. 请注意 ,由于原因,仅嘲笑SetupClass.functon_cannot_be_run_on_test_platform
并不能解决问题。
ATM, I figure the only way to get around this mess is to somehow override SetupClass.set_some_stuff
. 在ATM上,我认为避免这种混乱的唯一方法是以某种方式覆盖SetupClass.set_some_stuff
。 I cannot simply mock the entire class, because UUT
relies heavily on its other functionality as well. 我不能简单地模拟整个类,因为UUT
非常依赖于其其他功能。 I need everything to work as is, except this one method and I need that method to be able to access, self
in the same context as originally intend. 我需要一切都按原样工作,除了这个方法之外,我还需要该方法能够在与最初意图相同的上下文中self
访问。
I tried various things involving subclassing and mock.return_value etc. I'd rather not recall the pain that caused. 我尝试了各种涉及子类化和模拟.return_value等的事情。我宁愿不记得引起的痛苦。 :p :p
My kingdom for test-driven code in the first place! 我的王国首先是测试驱动的代码! This code contains a convolution of co-dependencies. 此代码包含一些相互依赖的卷积。 :-/ :-/
Apart from the multiple errors in the example code I wrote up off the top of my head at the cafe ... 除了示例代码中的多个错误外,我还在咖啡馆里写下了自己的头……
The problem was (mostly) that I was using return_value
instead of side_effect
to 'replace' the patched class with my own subclass. 问题是(主要是)我使用return_value
而不是side_effect
将修补的类替换为自己的子类。
My need, re-stated perhaps more clearly now, is to override a single method, set_some_stuff
, in a class within the unit under test (UUT) but without mocking the class. 现在,我可能需要更清楚地set_some_stuff
,我的需要是在被测单元(UUT)中的类中重写单个方法set_some_stuff
, set_some_stuff
该类。
The method issues several 'self.foo = bar' statements, which I want to change for testing purposes. 该方法发出多个“ self.foo = bar”语句,出于测试目的,我想对其进行更改。 Thus, mocking the method's (unused) return value is not enough ... and patch.object seems to lose class context, "'self' unknown" or the like. 因此,仅嘲笑该方法的(未使用的)返回值是不够的……并且patch.object似乎丢失了类上下文,“'自身'未知”等。
Finally , here is the working code, doing what I need ... 最后 ,这是工作代码,执行我需要做的...
import unittest
import mock
class SetupClass(object):
def set_some_stuff(self):
data_list = ['data not available', 'on test_platform'] # CRASH!
self.something = data_list[0]
self.something_else = data_list[1]
class UUT:
def __init__(self):
self.config = SetupClass()
self.config.set_some_stuff()
assert self.config.something == 'foo' # <-- used to crash before here ...
self.got_here = True # ... but now the override method from
# WedgeClass is being used! :=)
"""
Subclass the original class, overriding just the method in question. Then set
the subclass as the side_effect of the patched original, effectively replacing it.
"""
class WedgeClass(SetupClass):
def set_some_stuff(self):
self.something = 'foo'
pass # I'm a Python newbie, in too deep
class UnitTests(unittest.TestCase):
@mock.patch(__module__+'.SetupClass')
def test_UUT(self, mock1):
wedge_class = WedgeClass()
mock1.side_effect = WedgeClass # <--- Ureka! 'side_effect' not 'return_value' was the ley!
uut = UUT()
self.assertTrue(uut.got_here)
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