Take input and transform it into output is the fundamentals of programming. New developers often struggle with fundamentals and will usually only test the inpu

Take input and transform it into output is the fundamentals of programming. New developers often struggle with fundamentals and will usually only test the input they expect. Some one else has to intentionally give you bad input before you realise thats a thing people will do and something you need to think about. It doesn't help that most tutorials focus on getting output (yay results!) rather than focusing on how to get consistent transformation of input to output. The result is a lot of tutorials that focus on getting something done and forget / assume the fundamentals.