In working on the places tests, I've now seen multiple cases of the global idle-daily notification being triggered whilst a test is being run. The idle-daily could be one cause of intermittents that would be hard to find/diagnose, as this would be happening in the background with potentially no warning. For instance, bug 1382444 found that places maintenance was being triggered and would cause intermittents as it upset the database reading due to how the tests work (this wasn't a user-facing issue). I've also just been seeing various logs where the sqlite vacuum tries to kick in (although shouldn't be having an effect): https://treeherder.mozilla.org/logviewer.html#?job_id=132260679&repo=autoland&lineNumber=6234 I think we should do either: - Print a large console warning during tests if idle-daily is trigged - Disable idle-daily completely during tests (unless a test manually triggers it).

(In reply to Mark Banner (:standard8) from comment #0) > - Disable idle-daily completely during tests (unless a test manually > triggers it). ^-- this sounds like the right move to me, fwiw.

Comment on attachment 8914260 [details] Bug 1402248 - Disable idle-daily during mochitests to avoid possible background interactions that might cause intermittents. https://reviewboard.mozilla.org/r/185578/#review190522 would this make sense to do in: reftest xpcshell marionette web-platform-tests talos otherwise this looks like a great idea!

(In reply to Joel Maher ( :jmaher) (UTC-5) from comment #4) > xpcshell xpcshell is already mocking the idle service, so that a test that needs to actually test idle will have to invoke a special method to enable it. That change was made exactly to prevent intermittent failures related to idle.

(In reply to Joel Maher ( :jmaher) (UTC-5) from comment #4) > would this make sense to do in: > reftest > marionette > web-platform-tests > talos Talos was already done in bug 1383896. For the other three I think we could do, though I don't know if there is much benefit - they're not accessing the internals quite so much, and how sensitive are they to performance? In any case, I think it'd be an idea to land this and see how things go for a few days before doing more.

Pushed by mbanner@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/327dc39a53d8 Disable idle-daily during mochitests to avoid possible background interactions that might cause intermittents. r=jmaher