I always used a stout pole, about 1.5 inches thick and 5-6 feet long, blunt ended.
Jab the pole at the ice, straight down, with serious force. You are trying to pock it through the ice. If it does not go through, or crack the ice, the ice is good to walk on. Continue with the jabbing as you work your way across the ice. Ice almost always thins toward where it gets dangerous, so you should have warning.
Personally, I would never venture out to the middle of the pond/lake/livestock pool to tempt fate.
Me and cold water don't get along.