That puts a new spin on a “brittle unit test”

That makes sense, but to me that just means "keep dropping it until it implodes and then you can find out exactly how many dives it's good for". I still see absolutely no reason why humans should have been inside that thing. It's easy to criticize from an armchair, but goodness it just boggles my mind.

They did roughly that with the previous hull: it was used until it had to be derated. This accident was on the replacement hull which already had a few cycles on it... tested but supposedly not worn out.

Material science is hard, especially on a budget. This is definitely daredevil territory.

If it's a consumable, they should have tested at least one hull to destruction, just so they could be sure of it's failure modes.

Based on what I've seen, it doesn't sound like OceanGate had decided on a fixed number of dives. Instead they were planning to continually monitor it (x-ray scans after every dive and real-time acoustic monitoring during the dive) with the assumption that they would get some warning before it failed.