Toward the end of Wikimania I started working on some codesniffer stuff that could be run against extensions, skins etc to see if a change in mw-core has broken them.

My current WIP patch can be seen on gerrit and all comments are welcome! https://gerrit.wikimedia.org/r/#/c/153399/

My plan would be to have this run as a nightly job on jenkins across all extensions / skins in gerrit, thus everyday we would clearly be able to see if we had broken anything! The codesniffer stuff is also something that other extension developers could pull into their integration system (say using github and travis) and run across their extensions.