How do you tell that your unit tests are correct?

Question

I\'ve only done minor unit testing at various points in my career. Whenever I start diving into it again, it always troubles me how to prove that my tests are correct. How

Answer 1

First let me start by saying that unit testing is NOT only about testing. It is more about the design of the application. To see this in action you should put a camera with your display and record your coding while writing unit testing. You will realize that you are making a lot of design decisions when writing unit tests.

How to know if my unit tests are good?

You cannot test the logical part period! If your code is saying that 2+2 = 5 and your test is making sure that 2+2 = 5 then for you 2+2 is 5. To write good unit tests you MUST have good understanding of the domain you are working with. When you know what you are trying to accomplish you will write good tests and good code to accomplish it. If you have many unit tests and your assumptions are wrong then sooner or later you will find out your mistakes.