[Python-Dev] Allowing to run certain regression tests in subprocesses

[R. David Murray]

On Sat, 03 Aug 2013 16:47:37 -0700, Eli Bendersky <eliben at gmail.com> wrote:
> On Sat, Aug 3, 2013 at 4:36 PM, Eli Bendersky <eliben at 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.
> >
> > Thoughts?
> >
> > Eli
> 
> FWIW the problem is also discussed here:
> http://bugs.python.org/issue1674555, w.r.t. test_site

Can't you just launch a subprocess from the test itself using script_helpers?

--David