Over the past couple years I've tried unit testing in various projects. Sometimes successful, sometimes not. Even on those rare occasions when I've been successful I usually felt like I was going in circles with my tests, trying to figure out how to best build and organize them. Unit testing was more of a brawl than a ballet.
Several months ago I picked up what is now my second favorite book recommendation (right after Head First Design Patterns,) a gem called xUnit Test Patterns. If you're doing OOP, understand patterns, and want to improve your ability to deliver good software, this is the book to get. (There's even lots of information on the website if you don't want to purchase the book.)
The book is written for xUnit frameworks so it is a natural fit for JKI's VI Tester. There are a few minor things VI Tester currently doesn't let you do, such as inherit from a test class, but 96+% of the book is directly applicable to your Labview projects.