Programmer testing the new fully automated bar: orders 1 beer, 0 beers, -1 beers, calls it a day

Lead programmer: orders maxint beers, NaN beers, null beers

QA: purple beers, zzzzzzzzz...[x 2000] beers, 3 whiskey

User acceptance: orders burger on the rocks and beer with onions, takes mug out while still filling, swipes drivers license in credit card slot