With UAT IT tests I frequently have some or all of the following types of tests: smoke (the page get at the endpoint loads), happy, sad, optional and audit.
How many of these test types does it make sense to apply to unit tests and which make sense to add? For example if I make sure the caller of a method doesn't pass a null and always passes an array, does it make sense to have unit sad tests for null, invalid, etc for what is passed. Should we have them now because that is possible in the future and we might not realize to add them then?
Currently I am thinking I have just happy and 1 sad test for unit tests. That would also be based though on small functions that do one thing. Wondering what advice others could give for unit test types?