"Testing does not prove it works" (please correct me if I am misquoting). One might counter this with:
"Designing carefully does not prove it will work"

Of course not, but reliability can not be tested in, it can only be designed in.

I have seen many cases where something was thrown together with no deliberation, "we can test the bugs out". Such a design will never be totally reliable. If however sufficient time is spent on the design, the bugs found will more likely be benevolent (the stuff does not work) than diabolic (the stuff stops working once a month)

Anyhow, my basic beef is that when someone says "I tested the prototype, it can not be my fault that the next build does not work" which is uttely ridiculous.

Succesful testing does not prove the abscence of bugs, it only proves the abscence of known bugs.

Erik