How to make sure the toilet bowl won't break after abuse?
I'd try giving the main contractor (the person you're paying) a stern earfull about how you don't want their workers using your brand new toilet as a step-stool. Maybe say something like if you catch them doing it again you're not paying for that toilet, or they're fired, etc.

They're supposed be professionals and use ladders and stuff, besides the idiot worker could easily fall &amp; hurt himself and your property. 

Plastic wrap won't really protect porcelain from much more than dust, a dirty boot with a rock in the bottom could easily scratch it. Might even want to unwrap it some &amp; carefully inspect the "stepped on area" for any hints of damage. Do be careful not to scratch it yourself though, especially if any workers are watching, even a sharp bit on a ring, or house key, or piece of rock on your hands could scratch it, and if it is scratched you could demand it be replaced since it is damaged.



I'm quite sure that porcelain is only broken when it's cracked, so if you don't see any cracks it isn't broken. Toilets are really very sturdy, they're supposed to hold the heaviest people who use them, and almost everyone drops closed heavy toilet seats (even though they probably shouldn't). The next time someone's throwing out an old toilet, ask if you can smash it up with a hammer, you'll find they're quite sturdy (the local garbage here will accept broken porcelain in a box for no charge, but wanted $10 to take a whole toilet).

Just an idea, but there are some special dyes used for detecting cracks in metal, I suppose you could try using one of those on the toilet.

You could try using a stainless steel toilet if you really don't like porcelain, though I'd imagine it would be a lot more expensive, just from it's rarity, or maybe an RV or boat toilet (plastic or metal) is another option. You're also always sitting on the plastic/wood seat, that's on top of the toilet, so even if the toilet cracks you should still be on the seat anyway...