We had a caravan which was lent to some one who damaged the brakes, we had two other caravans at the time, and some one came knocking the door of my son offering to buy it, since surplice to requirements we said yes sell, the buyer was told brakes faulty, we expected he would either repair before taking or use a car trailer, but he simply towed it without brakes.
Some where near Bala he came from, once paid for we could not stop him towing it only option would be phone Police which did seem a bit sneaky so we didn't.
However as yet no MOT for caravans, so we really don't know how good or bad the brakes are, with old caravans one could try reversing without reversing stop in place that would test them, but there is really no way to test brakes on a modern caravan, OK can test hand brake but that does not really test over run brakes.