Robert Collins <robe...@robertcollins.net> added the comment: On Sat, 2009-04-04 at 23:06 +0000, Antoine Pitrou wrote: > Antoine Pitrou <pit...@free.fr> added the comment: > > > The main use case for addCleanup is resource allocation in tests. Why > > does this require clean ups to be executed before tearDown? > > If your cleanup relies on something which has been set up during setUp > and will be dropped during tearDown (a database connection, a temp dir, > an ssh session, whatever), then the cleanup must be run before the > teardown.
I don't think you can sensibly define an ordering between setup/teardown and cleanups that works for all cases. Either cleanups happen after teardown, and then you can use them when allocating things in setup/run/teardown, or they happen before teardown and you cannot safely use them except in run because things setup by a child will not have been torn down when cleanups run. [see the two where-it-breaks sequences below]. The issue is that cleanups are not connected to the inheritance heirarchy. They are safe and trivial to use with resources that are not connected to each other *however* they are defined, but the interaction with things being freed in tearDown cannot meet all cases unless you have per-class-in the-MRO-queues (which is overly complex). I assert that its better to be able to use cleanups in all three test methods rather than only in run, all other things being equal. Our experience in bzr (we use this heavily, and migrated to it incrementally across our 17K fixture suite) is that we rarely need to use cleanups on dependent resources, and when we need to it has been very easy to migrate the dependent resource to use cleanups as well. -Rob sequence 1: cleanup after teardowns prevents using cleanups on things freed in teardown: setup self.foo = thing() run self.bar = something(self.foo) self.addCleanUp(free, self.bar) teardown unthing(self.foo) cleanups free(self.bar) *boom* self.foo is already gone sequence 2: cleanup before teardown prevents using cleanups in base class setup methods base.setup self.foo = thing() self.addCleanup(unthing, self.foo) setup super.setup() self.bar = something(self.foo) run assertWhatever cleanups unthing(self.foo) teardown free(self.bar) *boom* self.foo is already gone ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue5679> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
