It's Time to Test the Emergency Breakaway Switch on Your Trailer

Again, testing this is a dead short across the 12v battery in the rig. If left energized too long the wires to the switch or the contacts in the switch will become very hot and cause the plastic case the switch is in to melt!

Actually a "dead short" is voltage to ground or neutral (same thing). The breakaway switch and it's branch circuit is a peripheral circuit energizes the electrical braking system exactly as the break controller would, with the exception that full 12 volts are supplied to the brakes instead of varied voltage from the brake controller. This will cause an effective brake application provided the brake pads are in good shape. The biggest downside would be a hard and quick battery drain due to the high current the brakes would use. Side affects could be brake coils burning out, and possibly the brake switch getting warm with prolonged energizing.

Here's an answer from an E-Trailer expert on your brake controller output voltages:

Mine accidently was triggered one time when I turned really sharp and it, only took less that 30 seconds for me to get out and try to re-insert the plastic safety key. In that time the switch body had begun to melt.