If your system has UAC enabled and you run VS normal/unelevated, the DisableHostNetworkConnection calls fail with:

System.ApplicationException: Failed to disable 'Ethernet 2' network connection. Return value is 5.
Make sure you're running the tests with elevated priviliges.

Could we mark tests as inconclusive instead of failing them in this case?
DisableHostNetworkConnection could use new Win32Exception(retValue), this would provide better error information.