[Python-ideas] Please consider adding context manager versions of setUp/tearDown to unittest.TestCase

[Chris Barker]

** Caution: cranky curmudgeonly opinionated comment ahead: **


unitest is such an ugly Java-esque static mess of an API that there's
really no point in trying to clean it up and make it more pythonic -- go
off and use pytest and be happier.

-CHB



On Tue, Aug 22, 2017 at 5:42 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On 22 August 2017 at 15:34, Nick Coghlan <ncoghlan at gmail.com> wrote:
> > On 21 August 2017 at 11:32, Neil Girdhar <mistersheik at gmail.com> wrote:
> >> This question describes an example of the problem:
> >> https://stackoverflow.com/questions/8416208/in-python-
> is-there-a-good-idiom-for-using-context-managers-in-setup-teardown.
> >> You want to invoke a context manager in your setup/tearing-down, but the
> >> easiest way to do that is to override run, which seems ugly.
> >
> > Using context managers when you can't use a with statement is one of
> > the main use cases for contextlib.ExitStack():
> >
> >     def setUp(self):
> >         self._resource_stack = stack = contextlib.ExitStack()
> >         self._resource = stack.enter_context(MyResource())
> >
> >     def tearDown(self):
> >         self._resource_stack.close()
> >
> > I posted that as an additional answer to the question:
> > https://stackoverflow.com/questions/8416208/in-python-
> is-there-a-good-idiom-for-using-context-managers-in-
> setup-teardown/45809502#45809502
>
> Sjoerd pointed out off-list that this doesn't cover the case where
> you're acquiring multiple resources and one of the later acquisitions
> fails, so I added the ExitStack idiom that covers that case (using
> stack.pop_all() as the last operation in a with statement):
>
>     def setUp(self):
>         with contextlib.ExitStack() as stack:
>             self._resource1 = stack.enter_context(GetResource())
>             self._resource2 = stack.enter_context(GetOtherResource())
>             # Failures before here -> immediate cleanup
>             self.addCleanup(stack.pop_all().close)
>             # Now cleanup won't happen until the cleanup functions run
>
> I also remember that using addCleanup lets you avoid defining tearDown
> entirely.
>
> Cheers,
> Nick.
>
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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>


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