David Hansen wrote:

In the House of Lords, at least a decade ago, they were discussing
the subject and one of the bods asked what tests were performed on
toilets. One of them got up and explained the ball of newspaper and
sawdust tests, which I hope are self-explanatory in this group.

I saw a video clip of a Japanese test once. They used modelling clay
mixed with expanded polystyrene, in eye-wateringly large bits. Much
better model than newspaper.

Andy