To use TypeMock in your unit tests you need to enable the typemocking engine.
TypeMock's documentation cites a few different ways to do this but doesn't provide an easy way to run the NUnit Gui alongside Visual Studio (which is the way I prefer to work) without running batch files which I find cumbersome.
Solution:
1) Be sure to install the Visual Studio AddIn when you install TypeMock - this should give you someTypeMock options in the Tools menu.
2) Enable TypeMock in Visual Studio using the 'Enable TypeMock.Net' option in the 'Tools' menu (if it reads 'Disable TypeMock.Net' then it's already enabled - which is the install default)
3) Create an external tools link to the NUnit Gui in the 'Tools' menu 'External Tools' option to launch the gui.
If you want to run TypeMock'ed unit tests just be sure to launch the gui from the 'Tools' link you created and TypeMocking is enabled! You can now run your unit tests in the gui in exactly the same way as normal.
NB// Remember you can attach to the NUnit Gui process from Visual Studio if you want to debug your unit tests.