Start a window manager for tests

[rolandmas]

Hi, as a Debian maintainer I'm faced with running testsuites for many packages, and an increasing number of them include a GUI. pytest-xvfb is quite convenient in wrapping the starting and stopping of Xvfb, but some of the tests (especially those using Qt) also require a running window manager to work.
So far I've worked around that by removing pytest-xvfb and starting/stopping Xvfb then a wm by hand, but that goes against the flow. I would love if pytest-xvfb could be given an option to set up a wm before starting the tests (and tear it down afterwards). Possibly via an environment variable and/or a pytest.ini option, I'll happily adapt :-)
Thanks for considering!

[The-Compiler]

I'm a bit confused on what you need from pytest-xvfb for this.

For one, what do you mean with "require a running window manager to work"? In the easiest case (~any window manager needs to run), the reason is probably that the tests require newly opened windows to be focused, and I'd argue that is a bug in the tests (because depending on the WM/settings, this is not the case with real WMs either).

In the more complex case, the application needs an "automatable" window manager where it can tell the WM to focus a given window and such (also see qutebrowser/qutebrowser#1831). I think that's completely orthogonal to pytest-xvfb, though.

In any case, can't you just start a window manager of your choice as part of the tests (e.g. in a session scoped fixture)? Or is your use-case more something like a xvfb_launch = somewm (name tbd) so you can set that via pytest -o ... without having to patch the sources at all?

[rolandmas]

My understanding is that the authors of the apps I'm packaging run the testsuite on desktop machines, and the "headless" configuration isn't their primary focus. So to use current pytest-xvfb with a wm as a fixture I'd have to patch many tests. So I currently have to run start xvfb and a wm first, then run pytest without pytest-xvfb, then tear down the wm and xvfb. That's cumbersome, and I was sort of hoping for something like what you suggested, yes, where I'd just have to add one line to a config file and the rest would follow.

Actually, I'm working on a patch implementing that, with xvfb_windowmanager. In case you're interested here's the current state of my patch (based on Debian's 3.0.0, haven't tried 3.1 yet). Not quite sure about my testsuite, it's a work in progress.

0001-Add-xvfb_windowmanager-option.patch