Don't worry about it right now; you have a longish way before you get to the tests? :-) It's like worrying about your Advanced Diploma when you're only 14 and starting?

Here in the States they can be used but I think mostly by the huge firms and I'm sure there are many other factors when considering you for a job, just like there are more factors for University than just what grades you got. I would think of it as a "placement" tool for them so they don't put you with opposite personalities? And in beginning jobs you aren't expected to be "professional" yet, that doesn't happen until after quite a bit of on-the-job experiment.

Actual jobs aren't very much like school and don't "use" what you learn there. Most of school is getting your head in a place where it's able to think about problems in a useful way, approach problems in a way that can hope for solving them. You won't really know anything much when you get out (my husband an electrical engineer says). I've never had a job specifically use anything in my couple of degrees?

If you are worried about how you'll do in certain areas, then hone those areas! You've got your music, work with people there and talk to them, get to know them and "practice" with them so you aren't as shy? You do know how to work together and can "prove" it because of your music! I can't think of a place one has to work "together" as a "team" more, can you? Any chance you can join a chamber group or something smaller than you're in? You can point to that in job interviews as a team and impress heck out of the employer I bet.

Here, see if this reassures you a little? http://www.psychometricadvantage.co.uk/