A pull test can be done anytime you are stopped. Just pull the pin and try to drive forward, you will feel and see the wheels on the trailer drag. If one spins while the others drag you need to adjust the brake and/or check the wiring, magnet, etc.
I also test the break away circuit when I have the tires elevated to adjust the brakes each year. All the tires should have about the same resistance to spinning, if the brake magnets are working and are adjusted correctly. It is also a good time to check the wires, plumbing, underside, etc. for problems while I am under the RV.