And then you accidentally crashed the whole business, for months, also known as a career limiting move. The stuff The Daily WTF published for failed companies.

Which is why only independent contractors can safely pull it off, and even then not always.

The correct test is targeted error injection. Make the thing a bit flaky see who complains or notices. Fan favorite is explicitly laggy or busted routers in the path for networked hardware. It's still not without risks, crappy old glue or scripts tend to fail catastrophically. So as usual, backups and spares. Documentation before messing with the thing...