Spin the egg on a flat surface; a boiled egg spins smoothly and steadily
Check the shell; a boiled egg feels firm, not sloshy
Shake the egg gently; a boiled egg does not move inside
Place the egg in water; a boiled egg usually sinks and lies on its side
Tap the egg lightly; a boiled egg sounds solid
Peel a small spot; a boiled egg has firm white and yolk
Cut the egg open; a boiled egg has fully set white and yolk