在python中测试副作用 [英] Testing for side-effects in python

问题描述

我想检查我的函数是否没有副作用，或仅影响精确变量的副作用.是否有一个函数可以检查它是否实际上没有副作用(或仅对某些变量具有副作用)?

I want to check that my function has no side-effects, or only side-effects affecting precise variables. Is there a function to check that it actually has no side-effects (or side-effects on only certain variables)?

如果没有，我该如何编写自己的代码，如下所示:

If not, how can I go about writing my own as follows:

我的想法是这样的，初始化，调用被测函数，然后调用最终方法:

class test_side_effects(parents_scope, exclude_variables=[]):
    def __init__():
        for variable_name, variable_initial in parents_scope.items():
            if variable_name not in exclude_variables:
                setattr(self, "test_"+variable_name, variable_initial)
    def final(self, final_parents_scope):
        for variable_name, variable_final in final_parents_scope.items():
            if variable_name[:5] is "test_" and variable_name not in exclude_variables:
                assert getattr(self, "test_"+variable_name) is variable_final, "Unexpected side effect of %s from %s to %s" % (variable_name, variable_initial, variable_final)

#here parents_scope should be inputted as dict(globals(),**locals())

我不确定这是否正是

I'm unsure if this is precisely the dictionary I want...

最后，我应该这样做吗?如果没有，为什么不呢?

Finally, should I be doing this? If not, why not?

推荐答案

我对编写测试所用的嵌套函数测试库并不熟悉，但似乎您确实应该在此处使用类(例如，在许多框架中都是TestCase).

I'm not familiar with the nested function testing library that you might be writing a test with, but it seems like you should really be using classes here (i.e. TestCase in many frameworks).

如果您的问题与在TestCase中获取父变量有关，则可以得到__dict__(对我而言，您所指的父"变量不清楚.

If your question then, is relating to getting the parent variables in your TestCase, you could get the __dict__ (It wasn't clear to me what the "Parent" variables you were referring to.

更新:@hayden发布要点以显示父变量的使用:

UPDATE: @hayden posted a gist to show the use of parent variables:

def f():
    a = 2
    b = 1
    def g():
        #a = 3
        b = 2
        c = 1
        print dict(globals(), **locals()) #prints a=1, but we want a=2 (from f)
    g()
a = 1
f()

如果将其转换为字典，则可以使用以下方法解决该问题:

If this is converted to a dictionary, then the problem is solvable with:

class f(object): # could be unittest TestCase
    def setUp(self, a=2, b=1):
        self.a = a
        self.b = b

    def g(self):
        #a = 3
        b = 2
        c = 1
        full_scope = globals().copy()
        full_scope.update(self.__dict__)
        full_scope.update(locals())
        full_scope.pop('full_scope')
        print full_scope # print a = 1

my_test = f()
my_test.setUp(a=1)
my_test.g()

您应该寻找已经实现了此目的的工具.我希望其他人将有一个已经实施的解决方案.

You are right to look for a tool which has already implemented this. I am hopeful that somebody else will have an already implemented solution.

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