Back in time I was working on an online trading card game, the integration test was running in the live server. (Don't ask me why. All I can say is that the ser

Back in time I was working on an online trading card game, the integration test was running in the live server. (Don't ask me why. All I can say is that the server had to be hastily built for some reason and it was known to be suboptimal in several aspects.) In order to avoid inference the test created tons of placeholder accounts and corresponding environments and it actually ran mostly well given the circumstances. One day I received a report that several accounts were simply disappearing and had to be re-registered every few days or so. I had to go through lots of recorded logs to determine what was happening: one of these accounts was named "Card" and some test was using it as a placeholder account, so it got removed when the test finished. How apt it is, that someone would use "Card" or similarly rare handles in a TCG. The testing infrastructure was updated to ensure that placeholder accounts can't coincide with actual accounts and affected users were compensated.