On 8 May 2014, at 22:02, Irving Reid <irv...@mozilla.com> wrote: > I've recently fought my way through a bunch of intermittent test > failures in the Add-on Manager mochitest-browser suite, and there's a > common anti-pattern where tests receive a Window callback, usually > "unload", and proceed to do significant work inside that event handler > (e.g. opening/closing/focusing other windows; see one detailed case at > https://bugzilla.mozilla.org/show_bug.cgi?id=608820#c281). > > The 'unload' event is signalled before the window is completely > unloaded; I don't know the fine details but the stack is in a state > where other window operations sometimes fail. > > Specifically, I found it a bit surprising that the "run_next_test()" > function in the async test harness starts the next test immediately on > top of the current JS stack, inside whatever callbacks are currently in > progress. > > I just filed bug 1007906 proposing that we modify the run_next_test > function in the mochitest framework to always schedule the next test for > a future spin of the event loop, to allow the stack to unwind - the > xpcshell test harness already does this, see > http://dxr.mozilla.org/mozilla-central/source/testing/xpcshell/head.js#1443. > > We should also update the MDN documentation about writing mochitests to > strongly advise making all DOM and Window callback listeners as small as > possible; my preference is to advocate using Promises as callback > listeners, because stack is always unwound before the .next handler is > invoked.
It looks like a good place to put this information would be as a subsection of https://developer.mozilla.org/en/docs/Mochitest#Writing_tests Can you add in a brief section covering this point, along with a brief code snippet illustrating a good and a bad way to do it perhaps? Just some rough notes would be fine; I’d be happy to edit it afterwards. Many thanks, Chris Mills Senior tech writer || Mozilla developer.mozilla.org || MDN cmi...@mozilla.com || @chrisdavidmills _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
