See http://www.codeproject.com/KB/aspnet/test-with-vs-devserver-2.aspx for a very lightweight and, in my biased opinion, elegant way to integrate webdev/cassini into your testing environment.
NOTE: the first example of controlling the .exe is for edutainment purposes only. Read through to the second, very brief, code sample for the money shot.
Update:
I use the technique listed above with nunit and most every unit test runner around, including continuous integration on servers that I do not control, extensively with great results.
When I need to simulate a real server with a host name and non-loopback ip address, which WebDev.WebServer and WebDev.WebHost cannot do,
- I add the host name to my hosts file, e.g. localhost.skysanders.net 192.168.0.10
- use the CassiniDev .dll in almost exactly the same way
it is so simple and bullet proof it should be illegal. ;-)
CassiniDev is also a perfect replacement for the WebDev.WebServer.exe for VS 2008/2010. It has integrated traffic monitoring and is quick a bit faster, both at startup and at processing.