in reply to Testing in real life

Another mantra you might keep in mind for any reasonably complicated enough program or module is "when your tests do not fail, you have not tested enough".

Remember that when all your tests pass, all you have proven is that your test cases pass and that all things you did not test are likely to fail (and probably at the worst possible moment).

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

In Section Meditations