You're feeling pretty good. Your latest embedded whiz-bang sailed through unit testing without a hitch, the marketing folks are touching up their launch plans, product literature is at the printers, and the sales department has announced a release date.
Life is good.
Time to get caught up on that backlog of e-mail messages. Preliminary testing shows evidence of a memory leak. So much for your good mood. Programming errors that occur only during run time can be very difficult and time-consuming to locate. Often the cause of the error is far removed from the actual program failure.