In a recent post to his site Freek Van der Herten talks about "handcrafting mocks" in your unit testing. In his example he shows the creation of custom mocks rather than using one of the current mocking test tools.

In an application I was working on I wanted to implement automated tweets. Of course, this logic should also be tested. In this blogpost I'd like to show you how you can easily handcraft your own mocks.

In his application, he wanted to be able to send tweets to Twitter when certain events happened. He starts with a bit of set up showing how to use this library to set up the OAuth connection between your application and Twitter account. He then shows the class that will make the actual tweet and how to use event handling to send the message when a new blog post is published. With this all in place, he starts in on the testing, showing the creation of the custom mock (so tweets aren't actually sent) and how to use it to test that a tweet was sent. He finishes the post with a mention of a possible refactoring: using an interface instead of extending a class to make the testing more structured.