[pytest-dev] pytest-xdist-1.11: restarting crash nodes, fixture cache fix

Anatoly Bubenkov bubenkoff at gmail.com
Mon Sep 22 22:31:00 CEST 2014

+1 for making tear downs consistent and clear for all the scopes
Having teardown argument solves it to me
On Sep 22, 2014 10:03 PM, "Andreas Pelme" <andreas at pelme.se> wrote:

> Hi Holger,
> On 19 sep 2014, at 09:52, holger krekel <holger at merlinux.eu> wrote:
> > I presume that with module and class scope people don't presume that
> > a fixture survives until the end of a process so eager teardown is less
> > of a problem, there, right?
> I have not fully grasped how fixture teardown currently happens in pytest.
> To explore it, I came up with this example:
> import pytest
> @pytest.yield_fixture(scope='class')
> def fix():
>     print 'fixture setup'
>     yield
>     print 'fixture teardown'
> class TestFoo():
>     def test_a(self, fix):
>         print 'test_a'
>     def test_b(self):
>         print 'test_b'
>     def test_c(self, fix):
>         print 'test_c'
> It gives me the output (with the latest pytest from PyPI):
> fixture setup
> test_a
> test_b
> test_c
> fixture teardown
> I.e. even though test_b does not actively request the fixture, it is
> active during the test.
> Is this even considered to be a bug or a feature? :-) This behavior may be
> considered a bug since it makes test suites brittle - if the fixture does
> not contain a value itself, it can probably be neglected to actually
> properly request the fixture, but test_b will still accidentally have “fix”
> available. Bugs like this will only show itself when running a subset of
> the test suite (and with xdist!).
> I would prefer (I think) if all fixtures where torn down when they are not
> requested (in my example, before test_b is run, to ensure test_b is only
> run with its own fixtures).
> However, if all teardowns worked like this, the efficiency will be very
> bad since there will be a lot of teardowns. I think these fixtures that
> should be allowed to stay alive, should be explicitly declared like that,
> like the option to pytest.fixture() suggested earlier.
> I think this makes sense regardless of whether the fixture is class,
> module or session scoped. Having different semantics depending on the scope
> would be confusing. Fixture authors must be aware and decide whether or not
> a fixture may accidentally be available to wrong tests. I have a hard time
> to see how we can solve this properly without a flag or some kind of
> distinction for this.
> I am probably missing a lot of details here, what are your thoughts on
> this?
> Cheers,
> Andreas
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