This is a question about puzzle-building. I very much enjoyed (albeit not solved) the puzzle Find the missing elephants by GOTO 0. And, as it is often the case with intriguing puzzles, it sparked some ideas of my own. (No need to worry, I'm not planning to put tons of clones online anytime soon...)
However, I then asked myself: How does one best build and verify such puzzles? Simple kernel-convolution puzzles I would have a good idea how to build & test, but anything with a complex conditional like in this particular puzzle, I don't know.
What tools/methods are you using/would you use to build such puzzles?