[issue39029] TestMaildir.test_clean fails randomly under parallel tests

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

> I was always under the assumption that -j 4 runs tests in parallel

If you run one test file, even with -j1000, only one test file will be run in parallel :-)

To run the same file in parallel, you have to ask to run it more than once: "-j2 test_mailbox test_mailbox" or "-j2 test_mailbox -F" for example.

-F runs the same tests in a loop until it fails. It's a convenient way to run the same test in parallel to detect race conditions ;-)

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39029>
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