Test ASP.NET application for Windows Authentication for user which is not in domain

I am working on a ASP.NET application which uses Windows Authentication. It works fine with users who are in Active Directory. Each page of application has been accessed by different users which are assigned roles with SQLRoleProvider. My question is how can I test my application for users who are not in domain? Can I pass fake user name and password from my code to test it?

Please help me with this.

Is there is any way to do this?

Thanks.