I once flew a Robin HR200 with a hobbs on the electrics. I pointed out to the instructor doing the checkout that I could switch the master off. He just said "go right ahead"... and of course it kept running! So did all of the electrics. Turns out the master in that aircraft was just a battery master!
I did not have the presence of mind to pull the ALT circuit breaker as well, and indeed now do not remember if this was possible.