Dave Johnston goes in depth about designing Counter-Strike’s Dust. Iterating and testing has existed since the beginning of, well, creativity. And it was definitely critical for a 16-year-old in 1999:
The problem was I’d been treating this brand-new gametype as if it was one I knew already – Capture the Flag – except in this CTF mode the flag (the bomb) started at the Terrorist spawn. But defusal wasn’t Capture the Flag. In fact, it was so utterly different that hardly a comparison could be drawn. Placing the bomb in the CT spawn hadn’t even crossed my mind. I made the change, and sent it back for playtests.
Playtesting is an important stage of any map’s development cycle. Without it, there’s little way of knowing exactly how a map will play when faced with real people; real players who haven’t the intricate knowledge of the map that you have. It’s playtests that inform you of flaws that need fixing before release – if the map is even fit to be released at all.
I’d be horrified to see a count of how much time I spent inside Dust and Dust 2 in high school. Or even just last summer.