Real network service tests

The Man page for hobbit states that :

When checking websites, it is possible to not only check that the webserver is responding, but also that the response looks correct by matching the response against a pre-defined pattern or a checksum

Can anybody tell me how to configure this? I want to run a http test on a webserver. If the webserver does not return the response I am expecting then alert me that something has changed on the server.

regards

Brian