I have been investigating this topic for the past couple of days. Not much progress, but some interesting things to note.

1. It might be an illuminating experience to use .NET Reflector to disassembly and study the unit test type implementation. The relevant assemblies are

Microsoft.VisualStudio.QualityTools.UnitTestFramework
Microsoft.VisualStudio.QualityTools.Tips.UnitTest.Adapter
Microsoft.VisualStudio.QualityTools.Tips.UnitTest.AssemblyResolver
Microsoft.VisualStudio.QualityTools.Tips.UnitTest.ObjectModel
Microsoft.VisualStudio.QualityTools.Tips.UnitTest.Tip
Microsoft.VisualStudio.QualityTools.AgentObject
Microsoft.VisualStudio.QualityTools.ExecutionCommon
Microsoft.VisualStudio.QualityTools.Common
Microsoft.VisualStudio.QualityTools.Resource


2. Study the MyTest implementation provided in the Visual Studio SDK. Note that they have included some code that is related to the test project (the wizard and so on) that are not directly related to the test type implementation itself. This is the MyTestWizard class.

The MSDN documentation is sparse on this topic which is kind of frustating, but figuring this out should be fun.

Also, note that there are deploy.bat and undeploy.bat files in the MyTest sample which indicate what needs to be done in order to register and unregister a new test type.

However, my last attempt to register and used the MyTest sample failed which again, is kind of frustrating.

Update:

I managed to get the MyTest sample working. So, I will post a step by step account of how it seems to work in a subsequent post.