Assuming you have disk brakes, if you look through the tire rim you should be able to see rotors and calipers. Just like what is on your Pathfinder.
In the pic below, the caliper is painted red and this particular rotor is slotted and drilled. Yours likely has a smooth finish.
If you have brakes on both axles then you will see calipers and rotors on all 4 wheels. Some trailers only have brakes on one axle in which case you'll only see calipers and rotors on two of the wheels (one on each side).
I'm not sure of a great way to test the brakes without towing. I would try to find a large empty parking lot and start slow and get a feel for how much your stopping distance changes. Gradually increase your speed and try some hard barking as well. It's good to have a feel for it in case you have a panic stop on the road.
If you have brakes on both axles, the trailer isn't going to rely on the tow vehicle too much. With single axle you will feel it more. If it feels like the trailer is relying too much on the tow vehicle then maybe you want to have the brakes checked.
Oh, don't forget to post in this thread. http://www.thenissanpath.com/viewtopic. ... highlight=