Sounds more like a litmus or pregnancy test to me.
The best indicator of food safety should be smell. When you buy a piece of fish, it shouldn't smell like fish. If it don't smell good, don't eat it. (Right Buck?...)
Sometimes it's a judgment call. One time I found a plump $10 rib steak that had gone missing in the fridge for a few weeks. It was green and fuzzy. After a thorough scrubbing and wash, and a quick searing side to side...it was delicious. Just well aged imo. No adverse affects.
Well Bowser, go ahead and call it a dipstick if it makes you feel vindicated...