I heard from an officer (in my city at least) that part of their training is getting shot by a taser. They even let citizens who join their "explorers program" get shocked by one for the experience (clip on the ends, not shot).
I don't believe the trigger is depressed during this, so it's just the contact shock, not a prolonged/repeated one.
I also have no idea what medical personnel are on hand, but all police officers are trained in CPR and I'd imagine they have an AED on premises, even if there are no EMTs right there.
They should do the testing a 30 minute drive from the hospital without medical personnel on hand at the top of a flight of cement stairs with no one around to catch their fall.
I'm sure the police would not volunteer for that test.