For more context:
This is a group of volunteers who are also very experienced software QA testers. We're going to be hunting for bugs in the new design of login and account creation on Wikimedia Labs.
The next step, after that testing and any relevant bug fixing, is to enable the new look on an opt-in basis via a URL parameter, across the wikis. This will mean that editors will have the opportunity to test the new design on their home wiki and ensure there are no further bugs or problems with the localization, before we enable the changes as defaults.
Look for a blog post and testing instructions aimed specifically at Wikimedians in the following week or two. I'll be sure to post here as well, of course.