Using pytest, sometimes does not capture stderr

[Peter Otten]

On 05/04/2021 06:25, Cameron Simpson wrote:

> If you truly need to test msg() _without_ the file= parameter, you could
> monkey patch module_2:
> 
>      old_MSG_DESTINATION = module_2.MSG_DESTINATION
>      module_2.MSG_DESTINATION = sys.stderr
>      # now the module_2 module has an updated reference for sys.stderr
>      ...
>      msg("a", "message")
>      ...
>      module_2.MSG_DESTINATION = old_MSG_DESTINATION
>      # normality restored

I was about to write "use contextlib.redirect_sterr()", and noted my 
error just before hitting send. There is a tool in the stdlib that might 
work though:

from unittest import mock

with mock.patch("module_2.MSG_DESTINATION", sys.stderr):
     msg("a", "message")