Flow tests run on CloudBees/Sauce Labs occasionally fail with "failed insert" editing an existing post. Overlapping test sessions may attempt to edit the same topic or post on the Talk:Flow_QA board, which leads to an edit conflict.
It would be better if the test edited a known topic or post rather than the first one on the Flow board. Previous feature tests create topics and posts, so (commence handwaving...) the edit_existing test could take an optional parameter naming a particular text string or item ID to edit The alternative is for the test to handle edit conflict, but it's a rare occurrence so the code would be untested until it breaks.
A related minor enhancement: to aid debugging issues it would be nice if edit strings like "Post edited0.2921675098405858" included the BROWSER_LABEL.