[Python-Dev] r86570 - in python/branches/py3k: Lib/unittest/case.py Lib/unittest/test/test_case.py Misc/NEWS

[Michael Foord]

On 20/11/2010 15:59, Antoine Pitrou wrote:
> Le samedi 20 novembre 2010 à 15:48 +0000, Michael Foord a écrit :
>> On 20/11/2010 15:42, Antoine Pitrou wrote:
>>> On Sat, 20 Nov 2010 16:34:26 +0100 (CET)
>>> michael.foord<python-checkins at python.org>   wrote:
>>>> +
>>>> +    def testPickle(self):
>>>> +        # Issue 10326
>>>> +
>>>> +        # Can't use TestCase classes defined in Test class as
>>>> +        # pickle does not work with inner classes
>>>> +        test = unittest.TestCase('run')
>>>> +        for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
>>>> +
>>>> +            # blew up prior to fix
>>>> +            pickled_test = pickle.dumps(test, protocol=protocol)
>>> You must also check that the object can be unpickled, otherwise
>>> making TestCase picklable is not only pointless, but misleading the
>>> user.  Other classes which claim to be picklable (such as e.g.
>>> io.BytesIO) are careful to check that unpickling works fine and
>>> produces an usable object.
>> Well, given the *particular* bug it is fixing, ensuring that the
>> TestCase instances can be pickled is enough. If they fail to unpickle
>> that is a bug in pickle and not in unittest.
> It wouldn't be, no.  pickle provides several different APIs to ensure
> that state gets correctly stored *and* restored, but it's up to
> application classes such as TestCase to ensure that they implement those
> APIs correctly for the intended behaviour.  Therefore, checking that
> pickling "works" fine (or, rather, seems to work) is only half ot the
> job.
>
> (for example, if you define a __getstate__, chances are you must define
> a __setstate__ too, and it is your job to make it work properly)

Yes, but unittest.TestCase doesn't implement any of those APIs (and if 
we did we would *definitely* need to test unpickling). That aside I have 
extended the test in the way you suggest.

Actually it would be nice to implement custom pickling / unpickling 
methods to allow Python 2.7 / 3.2 pickled TestCases to be unpickled on 
earlier versions of Python. I couldn't see how to change the class name 
in the pickle using the pickle protocol methods. Suggestions welcomed.

Michael

> Antoine.
>
>
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