That is not a proof by the CS standard though -- well, unless the job is defined as "write a program that processes these N test inputs known in advance", in wh

That is not a proof by the CS standard though -- well, unless the job is defined as "write a program that processes these N test inputs known in advance", in which case a program that prints the expected hardcoded output in response to each of the expected inputs and otherwise returns an error would be a good implementation :) I personally avoid using a word "proof" to mean anything other than a mathematical proof. It can be done with code, for sure, but as grandparent said, usually isn't.