python中无类型的单元测试？
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unittest for none type in python?
提问by peppy
I was just wondering how I would go about testing for a function that does not return anything. for example, say I have this function:
我只是想知道如何测试一个不返回任何内容的函数。例如，假设我有这个功能：
def is_in(char):
my_list = []
my_list.append(char)
and then if I were to test it:
然后如果我要测试它：
class TestIsIn(unittest.TestCase):
def test_one(self):
''' Test if one character was added to the list'''
self.assertEqual(self.is_in('a'), and this is where I am lost)
I don't know what to assert the function is equal to, since there is no return value that I could compare it to.
我不知道断言函数等于什么，因为没有返回值可以比较它。
EDIT: would assertIn work?
编辑： assertIn 会起作用吗？
回答by aquavitae
The point of a unit test is to test something that the function does. If its not returning a value, then what is it actually doing? In this case, it doesn't appear to be doing anything, since my_listis a local variable, but if your function actually looked something like this:
单元测试的重点是测试函数所做的事情。如果它没有返回值，那么它实际上在做什么？在这种情况下，它似乎没有做任何事情，因为它my_list是一个局部变量，但如果您的函数实际上看起来像这样：
def is_in(char, my_list):
my_list.append(char)
Then you would want to test if charis actually appended to the list. Your test would be:
然后你会想要测试是否char真的附加到列表中。您的测试将是：
def test_one(self):
my_list = []
is_in('a', my_list)
self.assertEqual(my_list, ['a'])
Since the function does not return a value, there's no point testing for it (unless you need make sure that it doesn't return a value).
由于该函数不返回值，因此没有必要对其进行测试（除非您需要确保它不返回值）。
回答by Kevin Christopher Henry
All Python functions return something. If you don't specify a return value, Noneis returned. So if your goal really is to make sure that something doesn't return a value, you can just say
所有 Python 函数都会返回一些东西。如果不指定返回值，None则返回。所以如果你的目标真的是确保某些东西不返回值，你可以说
self.assertIsNone(self.is_in('a'))
(However, this can't distinguish between a function without an explicit return value and one which does return None.)
（但是，这无法区分没有显式返回值的函数和有返回值的函数return None。）
