[Python-Dev] Tests failing on Windows with TESTFN
On 25/07/2018 16:07, Tim Golden wrote:
> One problem is that certain tests use support.TESTFN (a local directory
> constructed from the pid) for output files etc. However this can cause
> issues on Windows when recreating the folders / files for multiple
> tests, especially when running in parallel.
> Here's an example on my laptop deliberately running 3 tests with -j0
> which I know will generate an error about one time in three:
> C:\work-in-progress\cpython>python -mtest -j0 test_urllib2 test_bz2
[... snip ...]
> [...] I wanted to ask first
> whether there was any objection to my converting tests to using tempfile
> functions which should avoid the problem?
Thanks to those who responded here and/or on the two bpo issues I've
https://bugs.python.org/issue34239 -- test_bz2
https://bugs.python.org/issue34240 -- test_mmap
Two key questions have been posed in different ways:
1) Why are these errors occurring? ie are we dodging a root cause issue
2) Isn't this what test.support.unlink is there to solve?
For (1) I'm putting together a test run using code which I originally
wrote for https://bugs.python.org/issue7443 to force the issues out into
For (2), yes: test.support.unlink is supposed to solve that. But it's
either not doing enough retries etc. or it's missing a trick.
To be clear: my motivation here isn't some housekeeping or modernisation
exercise. I want to get a clear test run on a fresh build on Windows. At
present I never get that. I'd be interested to hear from other Windows
devs whether they have the same experience?