The interview process is rather long; it is conducted by two VPs (the one of your department and the one of HR), so getting them both in the same place at the same time is tough (teleconferencing is also used). They are looking to see whether you are the kind of technical person who is very personable, once you get to the in-person interview. The technical test focuses more on your problem-solving process than performance, though getting the major parts of it right is required.