A standard HR interview, followed by a design challenge. Just an advice, never ever take a design challenge, especially if their challenge involves a problem or a client that they're currently working on in the company. Protect your skills and don't give it away for free. For this process, I was asked to give a curriculum for a given topic, and produce mockups with that curriculum, and was only given a week to do it. Not fair, not even doable. Designers, beware.