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On 4 Aug 2013 12:03, "Eli Bendersky" <eliben@gmail.com> wrote:
\>
\> On Sat, Aug 3, 2013 at 6:59 PM, Nick Coghlan <ncoghlan@gmail.com> wrote:
\> >
\> > On 4 Aug 2013 09:43, "Eli Bendersky" <eliben@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