The first stage was a fairly unstructured Google Hangouts chat with a senior dev. Second stage was a take-home programming test. This test, while not especially challenging for an experienced developer, was rather long and open-ended.
I spent 2 hours on it, creating a solid backbone for the project including test cases and comments for what enhancements I'd make if I were to spend more time on it. I also didn't hide the fact that I'd only spent 2 hours on the project and that I was not pretending that it was at all finished.
The feedback seemed pretty unconstructive and mostly negative and focused on the things that were missing from my solution. I hear that they chewed through a number of candidates in a similar manner.