Open Bug 1962340 Opened 19 days ago Updated 7 hours ago

Intermittent /html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html | new-scroll-event-dispatched-at-next-updating-rendering-time - assert_less_than: The MQL change event should have been dispatched

Categories

(Testing :: web-platform-tests, defect, P5)

Product:
Testing
Component:
web-platform-tests
Type:
defect

Tracking

(firefox-esr128 unaffected, firefox137 unaffected, firefox138 unaffected, firefox139 affected, firefox140 affected)

Tracking Flags:
Tracking Status
firefox-esr128 --- unaffected
firefox137 --- unaffected
firefox138 --- unaffected
firefox139 --- affected
firefox140 --- affected

People

(Reporter: intermittent-bug-filer, Unassigned)

References

(Regression)

Details

(Keywords: intermittent-failure, regression, test-verify-fail)

Filed by: amarc [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer?job_id=505281742&repo=autoland
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/WCt5KSEaSYaL1193Q-jCAg/runs/0/artifacts/public/logs/live_backing.log
Reftest URL: https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/WCt5KSEaSYaL1193Q-jCAg/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1

[task 2025-04-24T07:11:31.204Z] 07:11:31     INFO - TEST-START | /html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html
[task 2025-04-24T07:11:31.205Z] 07:11:31     INFO - Run 5/10
[task 2025-04-24T07:11:31.206Z] 07:11:31     INFO - Closing window 6f8fadfe-4be2-43d8-b8d4-a90076b8dc3c
[task 2025-04-24T07:11:31.576Z] 07:11:31     INFO - 
[task 2025-04-24T07:11:31.576Z] 07:11:31     INFO - TEST-UNEXPECTED-FAIL | /html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html | new-scroll-event-dispatched-at-next-updating-rendering-time - assert_less_than: The MQL change event should have been dispatched after the first scroll event expected a number less than 189 but got 189
[task 2025-04-24T07:11:31.576Z] 07:11:31     INFO - @http://web-platform.test:8000/html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html:89:19
[task 2025-04-24T07:11:31.577Z] 07:11:31     INFO - TEST-OK | /html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html | took 372ms
[task 2025-04-24T07:11:31.578Z] 07:11:31     INFO - PID 1020 | 1745478691577	Marionette	INFO	Stopped listening on port 49314
[task 2025-04-24T07:11:32.125Z] 07:11:32     INFO - Browser exited with return code -15
[task 2025-04-24T07:11:32.126Z] 07:11:32     INFO - Closing logging queue
[task 2025-04-24T07:11:32.127Z] 07:11:32     INFO - queue closed
[task 2025-04-24T07:11:32.151Z] 07:11:32     INFO - Application command: /opt/worker/tasks/task_174547853227928/build/application/Firefox Nightly.app/Contents/MacOS/firefox --marionette --remote-allow-system-access about:blank -foreground -profile /var/folders/4x/n_lj6n7x5_sf87jt5w27w8cm0000jb/T/tmpauqpms_s
[task 2025-04-24T07:11:32.159Z] 07:11:32     INFO - Starting runner
[task 2025-04-24T07:11:32.762Z] 07:11:32     INFO - PID 1057 | 1745478692761	Marionette	INFO	Marionette enabled
[task 2025-04-24T07:11:32.969Z] 07:11:32     INFO - PID 1057 | 1745478692968	Marionette	INFO	Listening on port 49335
[task 2025-04-24T07:11:35.809Z] 07:11:35     INFO - TEST-START | /html/webappapis/scripting/event-loops/new-scroll-event-dispatched-at-next-updating-rendering-time.html
Flags: needinfo?(hikezoe.birchill)
Keywords: regression
Regressed by: 1944711

Sigh. Before landing bug 1944711 I did run the test locally multiple times (over 100 times?) on Linux, it didn't fail there. :/ On Mac, I did run the test just a couple of times on Safari. :/

Set release status flags based on info from the regressing bug 1944711

status-firefox137: --- → unaffected
status-firefox138: --- → unaffected
status-firefox139: --- → affected
status-firefox-esr128: --- → unaffected

Okay there are three new failures, all of them are same time stamps, for example;

The MQL change event should have been dispatched after the first scroll event expected a number less than 222 but got 222

So, I presume on Mac opt builds the test runs quite fast so that there's no time difference observed via performance.now().

I think adding an artificial while loop after receiving the first scroll event here would solve this failure; The while loop would be;

const startTime = performance.now();
while (performance.now() - startTime < 50) {}
Flags: needinfo?(hikezoe.birchill)

Set release status flags based on info from the regressing bug 1944711

status-firefox140: --- → affected
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