I've been working with C# for the last 2 years, and I've never done any unit testing. I just need to know what the objective of unit testing is. What kind of results do we expect from unit testing? Is code quality checked by unit testing? In my view, unit testing is the job of testers; if that is true, then as a developer why would I need to write test code if the tester does the unit testing? Why should I write extra code for testing? Do I need to maintain a separate copy of a project for unit testing?