I purchased an electric fence tester from the local Tractor Supply (a farm supply store) for just a few bucks (with 5 neon lights to show strength) which I use when building the fence but often loose track of it for day-to-day testing.
I use two methods (not counting touching the fence) to test the fence when I am too lazy to go find the tester. Near the fence charger (and at a number of other locations) I have one of those spring-loaded gate insulators. I simply unhook the gate just a little bit and look for an arc to jump the small gap. If the fence is shorted out somewhere, there will be no arc because the fence charger will not supply power into a shorted fence. The other method is to take my fencing pliers (or any metal tool with an insulated handle) and create a near-short between the fence and a metal fence post leaving a small gap. Again you will see the arc if the fence is working--a larger arc indicates more power, a small arc a little power.
Now my story... I have a 10-mile charger (quite a lot of power to drive that much fence wire). I unhooked my gate which left the fence unenergized so I would not get jolted when working on the ground near the fence. However, I was kneeling on the ground near the charger. All of a sudden, the top of my head came into contact with the wire coming from the charger to the fence and I got the full ten miles worth through the top of my head. It knocked my head into the corner post; it clenched my jaw shut and knocked me to the ground. I have a lot more respect when working near the fence now.
PS. If you think wearing leather gloves will insulate you, remember, cattle are wearing leather also. I have not been brave enough to try my theory.
Dale