Not often, thank the gods. I mainly repair and replace equipment and run wires and pipe. I'm not all that good with the chemistry side of it, but if you want to know how to fix a gas pool heater, I'm your man. Just don't get irate if I tell you it needs to be replaced.
Anyway, I've never seen pH tests for pools that go from 0-14. Typical pool pH tests go from 6-8 because anything above or below that range is considered extreme for pools.