Umbraco UserType.GetType Error/Problem is not an instance of an object

I was trying implement the creation of users from a csv file directly into umbraco and doing a unit test. Unfortunately it doesn't allow that functionality out of the context of the website, I only realised this after a few hours of trying to fiddle around. I am sure there is a way to do this in version 6, as they have the contentservice etc, but I am yet to find the answer, until then for testing this sort of functionality its going to have be driven through the website. If anyone has any ideas then please feel free to let me know. Thanks.