This is another in Robert's Getting Started series, where he provides an introduction to a topic that everyone knows about but not everyone is actually doing (or doing enough of). In this episode, part 1 of 3, Robert shows how to get started with unit testing in Visual Studio. The primary goal of unit testing is to take the smallest piece of testable code in an application, isolate it from the remainder of the code, and determine whether it behaves exactly as you expect. Each unit can be tested separately and can easily be tested over and over again.
You can find the sample code and demo scripts for the entire 3 part series here.