But if you don't have a meter,,,
Been doing it this way for probably 45 years and I have never blown a diode.
Have you ever blown one by doing it, or just heard that from somewhere?
The newer your car, and the more electronics on board, the more peril you put the system in. I won a sizeable bet, back in the 70's about this
When you lift a battery connection on a charging / running system, a voltage spike up into the 100 volt area appears on the system. That spike is perfectly capable of damaging electronics systems.
YOU WILL NEVER FIND this so called "procedure" in any book, manual, or classroom.
Moreover, it proves NOTHING. That's because this so called 'test' does not show what the alternator can actually output. It could ALREADY have 2 or 3 open diodes and be "sick" but working enough to pass this "test."