I would guess that even old school filament test light should draw no more than .25-2W power.

Testing is a few seconds.

If any modern circuit is designed that frail....i.e. designed to fail

Old style test light with an incandescent bulb not only will draw more current, but when you have it connected to the battery the tip will measure close to 12v unless it is probing a ground. That can fry logic/computer signals.

The 'digital' one will draw negligible current, and will not present a voltage to the point being checked.

At the price, I figure well worth replacing the old bulb type in your toolbox.

Dad, that is the most succinct explanation I've read. Thank you..