Possible bug in pytest --doctest comparison

[mirca]

In Python:

>>> -0.0 == 0.0
True

Whereas while running pytest --doctest-modules (version 3.0.7):

Expected:
    0.0
Got:
    -0.0

[nicoddemus]

Thanks @mirca.

I can't reproduce the problem though, either on master or in version 3.0.7. Could you please test using the latest version and provide a minimal reproducible example if the error still happens? Thanks!

[mirca]

I tested with version 3.2.1 as well and got the same error:

➜ pytest --doctest-modules test.py
================================= test session starts ==================================
platform darwin -- Python 3.6.2, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: /Users/jvmirca, inifile:
plugins: pep8-1.0.6, cov-2.5.1
collected 1 item

test.py F

======================================= FAILURES =======================================
____________________________________ [doctest] test ____________________________________
001
002 >>> import numpy as np
003 >>> - np.log(1)
Expected:
    0.0
Got:
    -0.0

where test.py is:

"""
>>> import numpy as np
>>> - np.log(1)
0.0
"""

[nicoddemus]

Thanks @mirca for the reproducible example.

I can reproduce the same error in pytest and also using the standard library's doctest:

"""
>>> import numpy as np
>>> - np.log(1)
0.0
"""

if __name__ == '__main__':
    import doctest
    doctest.testmod()

$python .tmp\test_doctest.py
**********************************************************************
File ".tmp\test_doctest.py", line 3, in __main__
Failed example:
    - np.log(1)
Expected:
    0.0
Got:
    -0.0
**********************************************************************
1 items had failures:
   1 of   2 in __main__
***Test Failed*** 1 failures.

pytest uses the standard doctest for test collection and comparison, so it is actually a bug in python's doctest module. I suggest to report this problem in Python's issue tracker.

pytest can't really do anything in this case, so I'm closing this.

[mirca]

@nicoddemus Thanks for following up on this.

[nicoddemus]

No problem 👍