[TIP] context manager and setUp/tearDown
Ned Batchelder
ned at nedbatchelder.com
Mon Feb 11 09:59:48 PST 2013
On 2/11/2013 5:38 AM, andrea crotti wrote:
> I created a context manager to create a temporary database to play
> around in couchdb, like this:
>
> __metaclass__ = type
> """
> Utilities functions manipulate the database
> """
>
> from couchdbkit import Server
>
> TEMP_DB = 'unit_test_database'
> LOCAL_URI = 'http://localhost:5984'
>
>
> class TemporaryDb:
> def __init__(self):
> self.server = Server(LOCAL_URI)
>
> def _remove_if_there(self):
> if TEMP_DB in self.server.all_dbs():
> self.server.delete_db(TEMP_DB)
>
> def __enter__(self):
> self._remove_if_there()
> return self.server.create_db(TEMP_DB)
>
> def __exit__(self, type, value, traceback):
> self._remove_if_there()
>
> Now I want to use it in my unit tests, and I have a "problem" which I
> already saw other times, how do I use it nicely with setUp/tearDown?
>
> This basically works but I don't like it very much..
>
> class TestCouchOo(unittest.TestCase):
> """Create a CouchObject and test storing the various values
> """
> def setUp(self):
> self.temp = TemporaryDb()
> self.db = self.temp.__enter__()
>
> def tearDown(self):
> self.temp.__exit__(None, None, None)
I have been in this same situation, and refactored my context manager to
be based on an object which I could then use with
unittest.TestCase.addCleanup(). But now I wonder about code like this
instead (untested):
class TestCaseMixin(object):
def setup_context_manager(self, cm):
val = cm.__enter__()
self.addCleanup(functools.partial(cm.__exit__, None, None, None))
return val
Then you can add this to a test case class, and use this:
def setUp(self):
self.temp = self.setup_context_manager(TemporaryDb())
and it will be cleaned up automatically
--Ned.
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