QUnit tests for jquery.makeCollapsible are often failing on Jenkins. I've seen this at least three times in the last week or so, most recently on https://gerrit.wikimedia.org/r/#/c/124051/ . Every time the failure was within the jquery.makeCollapsible tests (but I'm not entirely sure if on the same exact test).
This might be related to the fake timers being used in them.
Version: 1.23.0
Severity: major