WebDriver window manipulation tests should be passing in Firefox

[andreastt]

A quick look at https://wpt.fyi/webdriver/tests shows most of the window manipulation tests (minimize_window.py, set_window_rect.py, fullscreen_window.py, contexts/maximize_window.py) are timing out in Firefox. These tests (except for the user prompt child tests) are passing in Firefox in the Mozilla CI.

These tests require a window manager to run successfully on Linux, and I wonder what environment WebDriver tests are run under? I suspect maybe they run under Xvfb? In this case i would highly recommend we move off using Xvfb for Firefox and Chrome and use their headless modes instead.

[jgraham]

FWIW I would strongly prefer we run with a real WM running, so that we aren't testing for bugs in the headless mode.

[jeffcarp]

I suspect maybe they run under Xvfb?

That is correct.

Is there an easy way to use Webdriver + FF/Chrome headless modes? What are your thoughts on how to proceed?

[andreastt]

If we want to use a real WM I’d suggest something along the lines of this:

xvfb-run --auto-servernum --server-args '-ac -screen 0 1024x768x24' \
    openbox --startup '/home/ato/src/gecko/mach wpt /home/ato/src/gecko/testing/web-platform/tests/webdriver'

But to test that it is indeed the lack of a WM that is causing the test timeouts you can run the entire job with the MOZ_HEADLESS=1 environment variable set, which will cause Firefox to run in headless mode.