From what I remember (went to Epcot last year), Test Track is a lot less intense in comparison to flumes (ie. Splash Mountain) or rollercoasters. This is, of course, my own opinion. I don't recall there being any drops at all (someone correct me if I'm wrong).
The ride starts off by going through tests in a huge building. These tests include testing the brakes and suspension and whatnot. Basically you go on bumpy areas, go through hot and cold areas, and speed around corners. The final test is on the actual test track. I read somewhere that the speeds really aren't that high but because of the way it's done, it actually feels a lot faster than it is in reality.
The first time I rode it, I sat in the front and I had a lot of fun. I went on it again right after (it was early in the morning so there wasn't much of a line) and this time sat in the back. I'm not sure if it was because I rode it in such a quick succession or because I sat in the back but I finished that ride feeling slightly dizzy (and my hair was all a mess!). It took a minute or two to feel normal again. However, it wasn't enough for me to avoid the ride. I was willing to ride it again later in the day and would even ride it twice in a row if given the chance. Personally, I definitely preferred the first row because it gave me a better view of what was going to happen next.
I think the best thing for you to do is have a family member or friend, who knows you well, ride it first. That way they can give you an honest assessment. My dad, brother and I rode on TT first and when we came out, my dad was trying to convince my mom to go on it. Knowing how she is with sudden turns and speed, I told her not to because she avoids basically any kind of thrill ride.
I do hope that you can go on the ride because it is one of my favorite rides at Epcot! However, I understand that you need to know the "truth" of the ride (my mom is the exact same way). Just remember that this is just my assessment of it. Have fun at Disney!