[Python-Dev] Allowing to run certain regression tests in subprocesses (original) (raw)

R. David Murray rdmurray at bitdance.com
Sun Aug 4 14:44:51 CEST 2013

On Sat, 03 Aug 2013 19:04:21 -0700, Eli Bendersky <eliben at gmail.com> wrote:

On Sat, Aug 3, 2013 at 6:57 PM, R. David Murray <rdmurray at bitdance.com> wrote: > 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. testsite > > Can't you just launch a subprocess from the test itself using scripthelpers? >

I can, but such launching will be necessarily duplicated across all tests that need this functionality (testsite, test_all, etc)._ Since regrtest already has functionality for launching whole test-suites in subprocesses, it makes sense to reuse it, no?

In the case of test_site and test___all___ we are talking about running the entire test file in a subprocess. It sounds like you are only talking about running one individual test function in a subprocess, for which using script_helpers seems the more natural solution.

--David

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