To gain confidence during the SUL3 rollout, especially when quick changes are needed, we should improve the (currently nonexistent) browser test coverage for CentralAuth, both SUL3-specific and for authentication in general.

This is going to be tricky as all the interesting functionality relates to interaction between multiple wikis, which AFAIK isn't supported by Quibble. But even a set of tests that can be manually triggered on Beta or run locally would be quite useful. And maybe we could have a smoke test on Beta and/or in production.