I resisted, saying that checking of this kind was likely to lead to rejecting valid orders. My program made sure that the expiration year was greater than or equal to the current year. I tested a couple more cases and pronounced the program working. Since 01 is less than 96, the year that we were installing this check, my program rejected the card. Major business applications, e.g., in banking, usually go through at least six months of testing before deployment.
Big companies have departments in place right now with a separate test computer.
They generate some large test data sets. If there is a problem with a mainframe-style application, chances are that it will be noticed long before the year 2000. The same kind that we have now. Computer software does not work. Macintoshes and Windows 3.1 machines crash every few hours.