py.test command is not compatible with multiprocessing start-methods other than *fork*

[Nikratio]

Currently, it is not possible to use the py.test command to run tests that use the multiprocessing module with a start-method other than fork. This is because the py.test script generated by setuptools does not include a if __name__ == '__main__' guard:

$ cat /usr/bin/py.test-3
#! /usr/bin/python3

import sys
from pkg_resources import load_entry_point
sys.exit(load_entry_point('pytest==2.6.3', 'console_scripts', 'py.test')())

This means that as soon as a test tries to spawn a new process, this process starts executing the test-suite itself (the -s option is necessary to see the output of the second process):

$ py.test-3 test_mp.py -s
============================================== test session starts ==============================================
platform linux -- Python 3.4.2 -- py-1.4.25 -- pytest-2.6.3
collected 1 items 

test_mp.py ============================================== test session starts ==============================================
platform linux -- Python 3.4.2 -- py-1.4.25 -- pytest-2.6.3
collected 1 items 

test_mp.py F
[...]

This is easily rectified by using a custom py.test command:

$ cat run_test.py 
#!/usr/bin/python3
import pytest
import sys
if __name__ == '__main__':
    sys.exit(pytest.main([__file__] + sys.argv[1:]))
$ python3 run_test.py test_mp.py  -s
============================================== test session starts ==============================================
platform linux -- Python 3.4.2 -- py-1.4.25 -- pytest-2.6.3
collected 1 items 

test_mp.py hello
.

=========================================== 1 passed in 0.11 seconds ============================================

But it would be much nicer if the standard py.test command could be used.

[RonnyPfannschmidt]

that's an issue with setuptools/pip as well as multiprocessing - py.test does not make the scripts but use the entry-points feature that existed since way before multiprocessing

also the script should differ these days for 3 main reasons

a) pip creates a different script for wheels (recent releases have those)
b) there is .exe file support on windows
c) pip >7 caches wheels whenever it can

from my POV this is nothing py.test should fix on its own, this should be fixed in pip/setuptools

because proper script creation on win32 is a major pita, at least personally i don't want to be responsible for it

[nicoddemus]

Is there anything that can be done by py.test at all here? From @RonnyPfannschmidt's, explanation I gather that nothing can be done and we should close this. Is this correct?

[RonnyPfannschmidt]

Workaround might be something like pyhon -m pytest

[Nikratio]

Reported at https://bitbucket.org/pypa/setuptools/issues/443/