Really trivial code like getters and setters that have no extra behaviour than setting a private field are overkill to test. In 3.0 C# even has some syntactic sugar where the compiler takes care of the private field so you don't have to program that.
I usually write lots of very simple tests verifying behaviour I expect from my classes. Even if it's simple stuff like adding two numbers. I switch a lot between writing a simple test and writing some lines of code. The reason for this is that I then can change around code without being afraid I broke things I didn't think about.
