[TIP] cleanUp for unittest

Kumar McMillan kumar.mcmillan at gmail.com
Fri Apr 3 10:33:38 PDT 2009

On Fri, Apr 3, 2009 at 12:16 PM, Michael Foord
<fuzzyman at voidspace.org.uk> wrote:
>> Doesn't matter to me, but I'm wondering... why a list of functions?
>> --titus
> I should have listed the relevant issue: http://bugs.python.org/issue5538
> The idea is that as you allocate resources that need cleaning up, you
> push the corresponding clean up function onto the list. It is what trial
> uses.
> It sounds like a very simple system to me.

[one day I'm going to hack into Titus' mailman and set default reply
to "all."  you've been warned!]

The idea as I understand it is that you would build the list of clean
up functions dynamically.  I could be wrong though as I don't use
Trial much.


def setUp(self):
   self.db = ScratchDb()
   self.cleanUp.append(lambda: self.db.teardown())

   self.tmp = TempIO()
   self.cleanUp.append(lambda: self.tmp.destroy())

vs. one cleanUp method, which could get very ugly with all the if
statements you would need to ensure it is safe to clean up a resource
that may or may not exist:

def cleanUp(self):
   if hasattr(self, 'db'):
   if hasattr(self, 'tmp'):

the problem cleanUp solves that tearDown cannot currently solve is,
for example, this scenario : self.db.setup() succeeds but TempIO()
does not.  In today's world tearDown() would not get called so you
would be left with a database that was never torn down.

I am a big +1 on this feature.

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