A test that reveals a bug has succeeded, not failed.

More than the act of testing, the act of designing tests is one of the best bug preventers known.

Second law: The complexity barrier. Software complexity (and therefore that of bugs) grows to the limits of our ability to manage that complexity.

A good threat is worth a thousand tests.

First law: The pesticide paradox. Every method you use to prevent or find bugs leaves a residue of subtler bugs against which those methods are ineffective.

One of the saddest sights to me has always been a human at a keyboard doing something by hand that could be automated. It's sad but hilarious.

If the objective of testing were to prove that a program is free of bugs, then not only would testing be practically impossible, but it would also be theoretically impossible.