1320987 - test_session_zombification | Unable to restore focus, expect failures and timeouts

Status: RESOLVED FIXED

(Firefox for Android Graveyard :: Testing, defect, P2)

Description

[Geoff Brown [:gbrown]]

On every run of Android mochitest-chrome, an "Unable to restore focus" error is logged by the test harness following test_session_zombification (and continues for all subsequent tests).

[task 2016-11-29T11:55:18.360205Z] 11:55:18     INFO -  138 INFO TEST-START | mobile/android/tests/browser/chrome/test_session_zombification.html
[task 2016-11-29T11:56:58.216413Z] 11:56:58     INFO -  139 INFO TEST-OK | mobile/android/tests/browser/chrome/test_session_zombification.html | took 91708ms
[task 2016-11-29T11:56:58.216509Z] 11:56:58     INFO -  140 INFO Error: Unable to restore focus, expect failures and timeouts.

This does not cause a test failure and mochitest-chrome is generally green, but there are low-frequency intermittent crash reports for mochitest-chrome, during and after test_session_zombification - bug 1319196. The crashes are actually aborts, caused by the test harness when it cannot determine the foreground application ('adb shell dumpsys...' times out).

I don't know why dumpsys times out, but it seems well correlated with "unable to restore focus", so I want to see that investigated and eliminated if possible.

https://hg.mozilla.org/mozilla-central/annotate/8387a4ada9a5c4cab059d8fafe0f8c933e83c149/testing/mochitest/tests/SimpleTest/TestRunner.js#l312

Comment 1

[Geoff Brown [:gbrown]]

:JanH -- Can you look into this?

Comment 2

[Jan Henning [:JanH]]

After a wild goose chase because I had no real idea how to interpret that focus error, I've finally hit the solution: 

I was relying on the cleanup functions to close the test tabs immediately after each subtest. In practice however, those cleanup functions only run at the very end of the test, after *all* subtests have run. This means of course that during the second subtest, I was overwriting the tab references to the tabs opened during the first subtest and consequently leaking and never closing them.

Because of this, the test harness tab then ended up in the background and couldn't be focused properly.

Comment 3

[Jan Henning [:JanH]]

Attachment: Bug 1320987 - Stop leaking tabs during test_session_zombification.

A subtest's cleanup function only runs at the very end, after *all* subtests have finished. This means that we cannot use it to close the test tabs if we want to reuse the tab variables during following subtests. If we did, we'd be leaking those previous tabs, meaning they remain open at the end of the test and cause possible problems for following tests as well as lots of "Unable to restore focus" messages in the log.

Review commit: https://reviewboard.mozilla.org/r/96652/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/96652/

Comment 4

[Geoff Brown [:gbrown]]

Comment on attachment 8815873 [details]
Bug 1320987 - Stop leaking tabs during test_session_zombification.

https://reviewboard.mozilla.org/r/96652/#review96964

This looks great. Thanks!

Comment 5

[Jan Henning [:JanH]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=c6c227f91b6ecb0104b487a1485b754038679abc

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ffd7e71624b5
Stop leaking tabs during test_session_zombification. r=gbrown

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/ffd7e71624b5