When submitting your code for testing, make sure you’ve got rid of all your debug messages, or the test suite will complain that your code is producing the wrong output, because diff is not intelligent enough to ignore lines like “W00t! It’s working!” and “Preparing to hack… hacking… hacked!”.
In other news, I got an error message today telling me I had insufficient magic in my pot. That was interesting.
I’ve had some perturbing error messages, including ‘Catastrophic error!’ and ‘Wrong! No prize for you!’