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

If other code guards against calling that method incorrectly, and no one else will be writing code to call that method, then I don't see a reason to test with invalid values. To me, it would seem a waste of time.