InvocationError when testing via tox but not via pytest called directly

[ixjlyons]

I've set up a minimally reproducible example as a repo here. The README explains how I've invoked the test using pytest directly and with tox, and I can't figure out why it doesn't work with tox.

If I've made an obvious error in my tox.ini somewhere, I'd appreciate finding out what to fix. This is the only place in the tox code that prints out the InvocationError without any other information except the command in question (what I'm seeing).

It should also be noted that I can run pytest-qt's tests with tox just fine. Also, if I comment out the test function's contents and remove the use of the qtbot fixture, the test runs fine with tox.

[The-Compiler]

Does adding passenv = * under [testenv] change anything? Can you install the pytest-faulthandler plugin and run pytest with -s and see if that gives you anything useful?

edit: My best guess would be that passenv = DISPLAY fixes this

[ixjlyons]

passenv = DISPLAY XAUTHORITY seems to do the trick (both required). Should a note about using pytest-qt with tox (I'm assuming also it's Linux-specific) be added to the docs?

@The-Compiler thanks a lot for the quick help by the way. This issue has irritated me for months and I only now put in a bit of time to produce a demo to try and get it resolved.

[The-Compiler]

You'll either need to do that or install pytest-xvfb then.

Unfortunately, Qt simply calls abort() on that error, and pytest's output capturing can't show the error to you as the process was just killed.

There's really not much we can do about this... I wonder if it'd help if pytest-qt disabled the output capturing while creating the QApplication though.

[nicoddemus]

@ixjlyons perhaps we can add a "Troubleshooting" sections to the docs, where we can mention both the "tox passenv" solution and the "abort()" issue?

[cauveryguda]

I am facing the same issue with tox. Tried placing passenv = DISPLAY XAUTHORITY under testenv in tox.ini but that did not help. Did your help on fixing this.

[The-Compiler]

@cauveryguda Is that with pytest? Can you run pytest with -s and see what's printed?

[reinjunon]

I have a similar problem. When running it live, your @The-Compiler your suggestion for passenv works. However, if i plan to integrate the test in the backend through jenkins, it fails with no error displayed.
ERROR: InvocationError for command '/var/lib/jenkins/workspace/se_thenewgui/.tox/py36/bin/pytest' (exited with code 1)

[The-Compiler]

Like I said above, you need a display server (or something like pytest-xvfb) to be able to run graphical PyQt applications.

[dvdblk]

Came across this issue without using QT. This error pops up when you have no tests defined in your test.py files.

Simply running pytest results in

$ pytest
========================================== test session starts ==========================================
platform linux -- Python 3.8.3, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: 
plugins: anyio-2.2.0, web3-5.19.0
collected 0 items                                                                                       

========================================= no tests ran in 0.01s =========================================
$

Running tox with a simple command = pytest setup results in:

========================================== test session starts ==========================================
platform linux -- Python 3.8.2, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
cachedir: .tox/python/.pytest_cache
rootdir: 
collected 0 items                                                                                       

========================================= no tests ran in 0.01s =========================================
ERROR: InvocationError for command ./.tox/python/bin/pytest (exited with code 5)
________________________________________________ summary ________________________________________________
ERROR:   python: commands failed

After defining at least one test function in tests/*.py the error no longer pops up.

[nicoddemus]

Hi @dvdblk,

That's standard pytest behavior: if it cannot find any test files, it will exit with error code 5, not related to pytest-qt at all.