First was online screen with some basic multiple choice test on C questions. Then phone screen with recruiter, recruiter copies down some answers to basic C++ questions. I actually almost flopped here due to how surprised I was at this process. The idea is the recruiter takes these answers and shoots them to an engineer for pass/fail evaluation. Give detailed answers and persistently ensure the recruiter writes down exactly what you want, don't worry about anything else like I did. The idea is to communicate with an engineer over and opaque recruiter, and as awkward as this might be, just do it well.
Got to the 6 hour online test. I'm pretty new to interviews (recently from university) and my expectations didn't really match reality. To anyone else that's on the socially unaware side like I am, this test can be pretty difficult in terms of communication. In my case I needed to implement data structures, and multiple different sorting algorithms (for different types of data), along with code to use these to solve a particular problem. The problem itself isn't too hard if communication is clear. The idea is that a test proctor is available over email. It's assumed that as an interviewee you take full advantage of the proctor and ask a lot of questions, and ask for meaningful advice. This is a no brainer to most, but some of us learn "the ropes" of interviews through experience.
As a specific example you're able to ask the proctor if you're headed in a good direction, or if he has a valuable suggestion or hint. It seems to be designed like a cheap business alternative to flying people over for in-person interviews. So treat the 6 hour test like an in-person interview and communicate a lot with the proctor.
Also be sure to be able to comfortably implement a range of data structures at-will. Trees, lists, vector, hash table, etc. Make sure to try to simplify the problem fully with the help of the proctor. In retrospect the test is pretty cool, and could have been a lot of fun. Just be sure not to be naive like me and assume these are like strict university "test proctors".