In this episode we are going to take at how to use Pex and Moles for .Net. Unit testing is great, but most free isolation frameworks require that your mocks implement an interface. But what do you do when the class you are trying to mock is static or sealed with no interface. If you canâ€™t modify the class then your unit testing efforts are usually stuck. Moles, the new free isolation framework from Microsoft, supports mocking almost any CLR based class (including sealed and static classes).