How do you tell if a toilet seal wax ring leaks if it does not flow out onto the floor? Not very easily until serious damage is done.   

My thought is toilet makers should make a a hole near the bottom of the toilet to insert an endoscope in to look for any leaks. The hole can be covered with a cap when not in use. A periodic inspection can save a huge expense if a leak is found.

Endoscopes are not that expensive. I have seen endoscopes that connect to smart phones. Also ones that have their own screen.

I have an endoscope that is used to inspect the inside of my ears having its own viewing screen. Paid something like less than $50.00 for it.