There's a few easy methods. First off, good luck stopping deer with that. They'll probably jump over it. Scent caps may help....maybe.
As for testing voltage, make sure your energizer is grounded good enough first. Ideally you have a volt meter for fences to check it, but if not....
Take an insulated jumper with the clips, connect one end to a short steel spike, fence, etc: a decent ground of some kind, not the energizer ground rod. Move the other clip towards the energized fence and try to watch for a spark. It should jump at least 1/4" from the wire to the clip. the same method can be used with a steel spike on a fence post (with an INSULTED grip).
If the wire isn't chewed up, it's probably physically okay. Not much else to check really.