Before I eat an egg, I always fill up a glass with water and gently place an egg in it. If the egg is really fresh it will sink to the bottom and lay on it's side - perfect!
If the egg sinks to the bottom, but only the tip touches, then it's still good to eat, but not super fresh. Note: most eggs I do the freshness test on fall in this range.
If however, the egg floats, DO NOT EAT it, it has likely gone bad and not safe to eat.
I check the freshness of my eggs as I cook rather than all at once - they could go bad after the test if sitting in the fridge for too long, so testing before cooking is best.