There are three possible solutions to your problem:
1. Run mocking_on.bat from TypeMock installation directory *before* running nunit. (Just like the error message suggests)
2. an even better way to run your tests is to run them from within the Visual Studio (this is what the addin is for):
Open the solution properties --> debug tab.
Check the radio button near "Start external program" and write the
full path to nunit-console.exe. e.g ("C:\Program Files\NUnit-Net-2.0
Under Command line arguments write the full path to the dll you are
trying to debug.
Now you can debug your tests by Right click the solution in the solution browser. Go to debug --> start new instance.
3. The best simple solution: Download and install TestDriven.NET from
This will allow you to set break point in the source file and start
debug session by right click on the source and choose Test with -->Debugger
Hope it helps