I won't really add much; everyone has pretty much explained well how the process works.

I got up to the phone interview and online assessment/test, but not onsite.

While the test was difficult, it was not really much more difficult than other online assessments I've had from other companies (IBM, Twitter, etc.).

The only thing I will add is that they still use most of the interview questions (especially programming) on CareerCup, under Epic Systems.

They are basically the exact questions. I really wish I knew this beforehand, since I got rejected. Oh well.

Look them up and study them. There are not really that many, to be honest.