Just in case anyone didn't know already - you can check the zap using a blade of grass. Grass conducts electricity but not particularly well, so if you hold a 6" blade of grass at one end and rest it on the electric wire, gradually move the bit you are holding nearer the wire until you feel a tingle. If you get your fingers to within 1" and still haven't felt anything then you can touch the wire directly without fear - there's not a lot of current there and you won't get much of a belt (or any.)
And because grass conducts electricity, it will allow the current to flow into the ground if growing blades are reaching the wire. So if the zap isn't as much as expected, check all along for anything touching the wire and earthing it.
Sorry to everyone who knew all this already - but I was so pleased when years ago someone told me about testing the fence with grass, I just had to pass it on.