Should I unit-test with data that should not be passed in a function (invalid input)?

Question

I am trying to use TDD for my coding practice. I would like to ask should I test with a data that should not happen in a function BUT this data may possibly break your progr

Answer 1

My answer is that, no, you don't want exceptions, you don't want to have to have ROBOT() check for out of range input. The clients should be so well behaved that they don't pass garbage values in.

You might want to document this - Just say that clients must be careful about the values they pass in.

Besides where are you going to get invalid values from? Well, user input or by converting strings to numbers. But in those cases it should be the conversion routines that perform the checks and give feedback about whether the values are valid or not. The values should be guaranteed to be valid long before they get anywhere near ROBOT()!