This winter I applied for a position with the second largest natural gas supplier here in Michigan. To echo what @TOXIC said, it is what it is. If this is your field of study just relax and you'll do fine.
The position I applied for was the same job I'm doing now, just with a different company. My testing started with an on line assessment test, then 2 weeks later at a testing facility I took three written tests, that dealt with like your math, science, problem solving, and a few other things. I had pre test jitters like most do but once I started I relaxed and found my groove and it was fairly easy.
The interview is where things went south for me. I was informed ahead of time by the company that their interview process uses the STAR format of questioning. If you're not familiar with this format check it out. From my research a bunch of large companies are using this format. The questions had absolutely nothing to do with the job at all. Basically this format is supposed to help this company see what kind of person/employee you are.
Long story short I totally bombed the interview and didn't get the job. I had the most experience and the most qualifications for this position and I'm a contractor and I already do the job as a contractor for the exact same company I applied for, but this STAR format said John Doe was more qualified and a better fit than me! Was a salty? Absolutely I was. It was a major blow to me, and knocked me down for a few days. A month and a half later I find out that after the new union contract was signed with this company the starting pay was less that what I'm making now. The benefits would have been better but I would have been bringing way less home because there's no overtime there, so it all worked out for the better.
I know this was long winded and I apologize but sounds like you're a detailed person like me. My whole point of this is I wouldn't focus so much on the testing. See if you can find out what the interview is going to consist of and if they use a certain format like the STAR format, then practice practice practice.