We need some way to defer an Accessibility crash test until some programatic point of time

[keithamus]

Currently the crash tests will wait for DOM Load event, and if they make it to that point the test is considered passing.

It's also possible to demarcate an element that needs to be in the DOM; if it is that is considered a pass.

For crash tests that test the accessibility engine, this is insufficient (at least for Gecko). Probably likewise focus tests or other tests where there is a multiprocess boundary, as it could take a variable amount of time to hit the right paths.

Of note web-platform-tests/wpt#53676 was added but is effectively useless for Gecko as the accessibility engine may start after DOM Load.

Ideally we'd have some way to denote to WPT/WebDriver that this test should remain open until some promise value is resolved, and only consider it passing if that resolved promise occurs. Perhaps we can make the existing routines generic to the same behaviour, such that there is a global promise value (e.g. window.crashTestResolved) that defaults to a Promise resolving on DOM load, and script can simply re-assign that value.

[cookiecrook]

I changed the name b/c this problem seems currently to be unique to accessibility crash tests, but the proposed solution seems more broadly applicable, so maybe my title change was a mistake... If you think it's not specific to accessibility, perhaps it should also be moved to another repo?