It is potentially disastrous to tow without brakes -- and against the law as Janet points out. Many brake controllers (and the Prodigy
certainly does) have a lever to test brakes (below 25mph) and set the calibration. It's easy to tell because the test lever applies the trailer brakes and not the tow vehicle brakes. You will need both a brake controller and the 7-pin umbilical connected for this; the circuit thru the umbilical is not complete unless you do have a brake controller.
Search the Forums on 'compass' -- I crawled under my Argosy and put a simple magnetic compass inside the wheel near the brake drums and had my wife push on the brake pedal (trailer not moving of course). The compass needle did swing about 10 degrees -- not large but enough to tell the brakes were trying to work -- later proven out by the Prodigy test lever application. You need a functioning battery system on the trailer for the breakaway switch to work -- but please note that your brake solenoids could burn out in under 5 minutes of constant application. So you could pull the breakaway lanyard for a test but put it right back in! This would allow a test without hooking up the umbilical.