1) If a test installation functions perfectly, all subsequent systems will malfunction.

1) If a test installation functions perfectly, all subsequent systems will
malfunction.
2) Not until a program has been in production for at least six months will the
most harmful error be discovered.
3) Job control instructions that positively cannot be arranged in improper
order will be.
4) Interchangeable tapes won't.
5) If the input editor has been designed to reject all bad input, a co-op will
discover a method to get bad data past it.
6) Profanity is the one language all programmers know best.
-- Troutmans's programming postulates