Otter Unit Test Framework is a tool which performs automated Unit Test in .NET 4,0 or above applications. It works similarly to the JUnit and it used as part of the application being tested, in MS Web or C# Developer 2010.
Older versions (00.05 and below) were developed for MS Visual Studio 2005 and can still be downloaded. For them, a MS Visual Studio Plugin was developed and in the project´s home page you can find its documentation.