Ummm... Being a C-10, I hope you're kidding about the whole jumper idea... It's one thing to use some #10 and put a 28A load on a 20A breaker to see if it'll trip, but intentionally dead shorting a circuit in an uncontrolled environment is just a bad idea...
If you have doubts about your breaker(s) functioning, I can tell you 2 breaker houses in your area that'll put em on their test bench and let you know if they work.
