Deliberately adding bugs to assess QA processes

Question

How do you know that as many bugs as possiblle have been discovered and solved in a program? Couple of years ago I have read a document about debugging (I think it was some sort of HOWTO). Among other things, that document described a technique in which the programming team deliberately adds bugs into the code and passes it to the QA team. The QA process is considered completed when all the deliberately known bugs have been discovered.

Unfortunately, I cannot find this document, or any similar one with description of this trick. Can someone please point me to such a document?

EDIT

To make Evgeny happy, let me paraphrase the last sentence of the first paragraph:

"The QA process isn't complete before all the deliberate bugs are found"

Answer 1

One name for the technique is 'Fault Injection'. One of the older books on the subject is 'Software Fault Injection: Inoculating Programs Against Errors' by Jeffrey Voas and Gary McGraw.

Answer 2

I've never seen such a document, but I'd be wary of saying the QA process is "complete" just because your deliberate bugs have been found. It's a good way of ensuring that your QA team doesn't get too lazy, but you can't really ensure they did enough testing.

It's fundamentally impossible to know that all bugs (or "as many bugs as possible") have been discovered. All you can do is follow a thorough, well thought-out testing approach to give yourself a good shot at it.