I think there are some different variations of the test, but essentially, they give you a drug that people with asthma will have a reaction to.
They gave me the drug five times, each time with a little bit more intensity. After each dose, I blew as hard as possible for as long as possible into a machine that recorded how it affected me. The rule is, if there is no more than a 20% change in your performance after taking the drug, then you dont have asthma.
I had some asthmatic symptoms when i was younger, but grew out of it at about age 12. The test was no problem for me. Just follow their instructions and try as hard as you can, and it will work out.
I got the test last year and passed. I didnt even need a waiver, they just got rid of the DQ.