Is there any way to test a breaker?

I had a separate circuit added to my garage to run my welder and my air compressor. (Not at the same time). My air compressor gives it fits and pops it on it's take up cycle. I had the compressor checked and they say it's fine. The compressor is an old old old Craftsman 2.5 hp 120v unit. I don't really want to get a new compressor, but I need air. How can I test my garage power to make sure I'm getting my juice?

OH, and burning down the garage is not an option. :)

Is the unloader working on the compressor? If not, the motor is trying to start against too much head pressure causing the motor to pull too many starting amps.