On 4 Aug 2013 12:03, "Eli Bendersky" <eli...@gmail.com> wrote: > > On Sat, Aug 3, 2013 at 6:59 PM, Nick Coghlan <ncogh...@gmail.com> wrote: > > > > On 4 Aug 2013 09:43, "Eli Bendersky" <eli...@gmail.com> wrote: > >> > >> Hi All, > >> > >> Today the issue of cross-test global env dependencies showed its ugly > >> head again for me. I recall a previous discussion > >> (http://mail.python.org/pipermail/python-dev/2013-January/123409.html) > >> but there were many more over the years. > >> > >> The core problem is that some tests modify the global env > >> (particularly importing modules) and this sometimes has adverse > >> effects on other tests, because test.regrtest runs all tests in a > >> single process. In the discussion linked above, the particular culprit > >> test__all__ was judged as a candidate to be moved to a subprocess. > >> > >> I want to propose adding a capability to our test harness to run > >> specific tests in subprocesses. Each test will have some simple way of > >> asking to be run in a subprocess, and regrtest will concur (even when > >> running -j1). test__all__ can go there, and it can help solve other > >> problems. > >> > >> My particular case is trying to write a test for > >> http://bugs.python.org/issue14988 - wherein I have to simulate a > >> situation of non-existent pyexpat. It's not hard to write a test for > >> it, but when run in tandem with other tests (where C extensions loaded > >> pyexpat) it becomes seemingly impossible to set up. This should not be > >> the case - there's nothing wrong with wanting to simulate this case, > >> and there's nothing wrong in Python and the stdlib - it's purely an > >> artifact of the way our regression suite works. > > > > I'm not actively opposed to the suggested idea, but is there a specific > > reason "test.support.import_fresh_module" doesn't work for this test? > > I'm not an expert on this topic, but I believe there's a problem > unloading code that was loaded by C extensions. import_fresh_module is > thus powerless here (which also appears to be the case empirically).
Sure, it's just unusual to have a case where "importing is blocked by adding None to sys.modules" differs from "not actually available", so I'd like to understand the situation better. Cheers, Nick. > > Eli
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