Blaze, I'd guess from your tone and style of questions that you are probably still at school.
You'll find, if you go and talk to the school careers people that Test Piloting is not an immediate career option - it's basically a follow-on career for people who are either very experienced pilots with a high degree of technical knowledge, or very well qualified Engineers who have built up the necessary flying experience and ability. In either case, they'll have spent a great deal of time training for all manner of emergencies, and all the peculiarities of handling aircraft in their particular class, whether that's high-g, high altitude, extreme cold, or whatever is particular to that operating environment.
If the area interests you, take a look at some of the threads linked from the sticky at the top of the flight test forum, but also the bottom line (at the schoolboy/schoolgirl stage) is that you should aim to get all and any flying experience you can (Air Cadets, Air Scouts, Gliding Club cadets - anything available) whilst pursuing all the mathematical and technical subjects you can to the best of your abilities.
But, it is one of the most exciting and interesting jobs n the world, and just because it takes years of effort to get into it, is no reason not to try.
G