How many unit tests should I write per function/method?

Question

Do you write one test per function/method, with multiple checks in the test, or a test for each check?

Answer 1

I try to separate out Database tests and Business Logic Tests (using BDD as others here recommend), running the Database ones first ensures your Database is in a good state before asking your application to play with it.

There's a good podcast show with Andy Leonard on what it involves and how to do it, and if you'd like a bit more information, I've written a blog post on the subject (shameless plug ;o)