How to know potato is done boiling without poking it to check softness?

I can never get potatoes boiled just right, they're either over or undercooked. When I think they could be about done, I poke one or two with a knife but then that one splits and cooks faster than others. It also spills the potato juices in the water and I don't like to do that, which is why I boil whole potatoes and not sliced.

Is there a way to know potatoes have attained just the right level of boiling without poking them with a knife or fork?