I mean, it's 5,000 volts at 100mA for the "high current" hi-pot or 20,000 volts at 10mA for the "high voltage" one or 40A AC @ 8V AC for the ground bonder. They do about what you'd expect: components pop, things arc, things arc a lot at 20kV, things smoke and then melt if you shove 40A through them.

It's more interesting when you break the tester itself. But then you have to fix the tester. These are not complicated machines (they're basically just transformers)... there's some complexity in regulating the outputs and more in making the measurements but most of the hard stuff is in having the tester itself survive the horrid abuse it's visiting on everything else around it.