You should have a slide switch or lever on your controller. This is the manual override. With the trailer hooked to the TV have someone slide it over when you spin the wheel. If the wheel comes to a halt, the brakes are working.
If you aren't aware of this slide or lever, you should read the directions for your controller. This is the switch that used to set your brake controller for manual override, and you will need it in emergency situations.
Caveat: If all else fails, read the directions.