(I should have created a task for this a loooong time ago but better late than never I suppose.)
Since the env-abstraction-layer branch contains substantial rewrites of mediawiki_selenium (see all the gory design details here), I'd like to go over it with those of you who are either writing or running browser tests before merging it to master. It's meant to be as backwards compatible as possible, but some of its behaviors might have implications for CI or test design.