Bugs lurk in corners and congregate at boundaries.

In programming, it’s often the buts in the specification that kill you.

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.

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

If you can't test it, don't build it. If you don't test it, rip it out.

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.

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