My sad testing/troubleshooting story involves a game with a lot of parser hacks. All my testers kept receiving a spurious “you’ll have to say which direction to go in” message every single turn. I would test the file, not find that, and mark it solved. Rinse, repeat.
What never occurred to me was that there might be a difference between the testing version of the program that I was running in the Inform app and the release version of the program that was created when I hit “release,” which was what the testers and my players were playing.
Turns out that one of the hacks would execute the first action in the library every turn. In testing versions this was a debugging action that didn’t do anything–in release versions this was the going action, without a noun, which produced the error message.
So definitely, you should run the release version of your game before you actually ship it.