Unit testing can be fairly straightforward, until you come to a class that uses an external service like emails, databases, file system, web service, or any other "slow" dependency.  Often these external services are slow, incorrect, or not working at all, reducing the value unit tests promised.  In this session, we'll take a look at the whys and hows of test double patterns such as mocks and stubs.  We'll cover how to use them effectively with and without tools such as Rhino Mocks.  Finally, we'll look at how we can take advantage of mocks and stubs to exercise all of the paths in our code, eliminating those pesky bugs that only seem to come up in production.