Problem
If you want to use the standard code coverage that comes with Visual Studio Team Developer to analyse any C# code within your BizTalk solution you will normally come across the problem that when you open the code coverage page within the test run config file the dialog closes itself.
This is a bit of a pain in the butt!!
Work Around
If you want to amend the code coverage page you can do this by temporarily unloading your BizTalk projects within the Solution Explorer. When all of the BizTalk projects are unloaded then you can edit the code coverage section of the test run config as normal. Then when you have done this simply reload your BizTalk projects.
This should help you effectively unit test the C# code in your BizTalk solution.