I found this in one of the article shared in fb and shame that I did not record the link which I could not give credit where it is due.
It was sharing that if you are planning for vacation or “away from home” for a duration of time and you have some frozen food which is crucial that it is maintained frozen, then this may be useful to detect if there was a cut-off with the power (probably for a day and it could have melt the food in the freezer).
To do that, take a cup of water and freeze it. Once it is frozen, take a coin and put in on top of the ice (frozen water). By having that, should the coin drop onto the bottom of the cup, it means there was time when the freezer was power off and the food might have became thawed and re-frozen. That can easily tell if the food should be thrown.
Hope that is useful for you if you are planning for a trip away from home.