Pop the egg in a jug of cold water. If it sinks to the bottom and lies down it’s fresh as they come. If it sinks but stands on end it’s still fresh and good for eating.
As the egg ages it will sit higher and higher in the water, so if it floats to the top it’s not fresh at all and so you might want to consider discarding it.
Why is this? It’s because of the amount of air in the egg. When eggs are super fresh they have just a tiny amount of air in, but then over time the amount of air in there increases, and that is what makes it float in the water.
Don’t just throw away your eggs just because you THINK they’re not good. Test them first.