Here's a VS2010 solution as it stands today, it is using Bricscad v14 lib's but you should be able to switch them out for AutoCAD with little work.
Tools required:
NuGet package manager should be installed in VS to manage the Nunit and Moq packages, this is a lot easier than loading all the requirements manually.
NUnit - download and install, I run it in the 'mini' setup which hides the output progress and messages, you can find the output by right clicking on the test to see any errors etc.
To run the tests in NUnit, start NUnit and go 'Open Project' and browse to the bin folder and select the dll with <ProjectName>.Tests.dll and you should be able to see and run the tests.
Repeat for the other test project/s.
<edit> Another confusing aspect of testing is 'how do you debug?', it can be done but really, the process of testing and running tests takes you straight to the problem if it fails anyway, you shouldn't need to debug at all, if you do your tests (or implementation code) have too much logic, another "code smell" if you like</edit>