Been a Fed for 12 yrs. and just don't remember a "test" like you seem to be using the word. I applied, submitted a resume, got interviewed, background/security checked, and accepted. I have heard that landing a CO job is a lot more competitive now than in 1990 and, I was, am, and was hired as, an electrician and an Officer. That being said, practically every permanent employee of the Federal Bureau is considered a LEO and will go to the Academy in Glynco, GA. As to the ? of carrying...NOT off-duty. It is NOT authorized to carry off-duty NOR WILL YOU EVER be authorized to carry a personal weapon. Most that desire to, at least in Florida, get a CCW from the State and carry that way. No one carries inside. Get a good night's sleep, be honest with your answers, and Good Luck.
Stay Safe.