Plasma is an in-process web server emulator that can be used for automation and unit testing of ASP.NET applications. Ok, so what can you do with it? Basically Plasma allows you to easily test or automate ASP.NET pages and applications in a performant manner, since everything occurs in-memory, so there is not network level overhead. Many of the web test scenarios available as part of Visual Studio Team Suite : Tester SKU are possible with this framework and therefore available to NUnit users (examples - testing that a page has a given value on it after a postback, testing that a page returns within a given time threshold, etc.).