Filed by: hskupin [at] mozilla.com https://treeherder.mozilla.org/logviewer.html#?job_id=95696166&repo=autoland https://archive.mozilla.org/pub/firefox/tinderbox-builds/autoland-win64-debug/1493659700/autoland_win8_64-debug_test-marionette-e10s-bm127-tests1-windows-build474.txt.gz So the reason here is an early return from click() because there is an unexpected hash change of the URL, which happens before the `pagehide` event is getting raises, and which indicates a full page load to the previous page in the cache: 1493662706798 Marionette TRACE 433 -> [0,19,"findElement",{"using":"id","value":"history-back"}] 1493662706808 Marionette TRACE 433 <- [1,19,null,{"value":{"element-6066-11e4-a52e-4f735466cecf":"4ecfd565-3c29-4673-a6a5-0ace3f05b311","ELEMENT":"4ecfd565-3c29-4673-a6a5-0ace3f05b311"}}] 1493662706810 Marionette TRACE 433 -> [0,20,"clickElement",{"id":"4ecfd565-3c29-4673-a6a5-0ace3f05b311"}] 1493662707111 Marionette DEBUG Received DOM event "hashchange" for "http://127.0.0.1:49326/clicks.html#" 1493662707131 Marionette TRACE 433 <- [1,20,null,{}] 1493662707159 Marionette TRACE 433 -> [0,21,"findElement",{"using":"id","value":"anchor"}] Given that we have a double navigation here, I'm not that sure if we should actually cover that by default. I will have a look at this today and do some timing tests, to see how this could be improved.

So this failure can actually happen for very slow machines under the following condition: 1) Clicking a link will cause a hashchange event to fire (eg. Javascript links) 2) A remoteness change will happen (nowadays only for about: pages, except about:blank) It's very unlikely that such a condition will happen in the wild. I will have to find a way to simply stop the `hashchange` event in our unit test.

Actually in clicks.html we have the following source: > <a href="#" onclick="history.back();" id="history-back">Back in browser history</a> It means the href value of '#' is actually adding the hash, before the real navigation starts. So we have a double navigation here due to the `onclick` listener. I don't think that we can support such a double-navigation right now, and I would suggest to simply drop that for now by removing the `#` from the href.

Comment on attachment 8863758 [details] Bug 1361302 - Fix clicks.html to not trigger a double navigation for history navigation. https://reviewboard.mozilla.org/r/135534/#review138646

Pushed by hskupin@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/f3d518ac621a Fix clicks.html to not trigger a double navigation for history navigation. r=automatedtester

Moving bug to Testing::Marionette Client and Harness component per bug 1815831.