I can sort of understand your worries. I myself have asthma, and I was made to run round the car park
. I don`t think that the actual test is that difficult to be honest. I think for your age, they will have a set level which you have to reach. However like Gingernut said, providing you don`t have an existing lung disease, you`ll be fine. Ohh and another point about running around the car park, my lung function got better after the run !!
Keep us posted on how your medical goes, I am sure you will be fine. They are all very helpful down there !!
Kiev23