"HtmlUnit is a java unit testing framework for testing web based applications.
It is similar in concept to HttpUnit but is very different in implementation.
Which one is better for you depends on how you like to write your tests.
HttpUnit models the HTTP protocol, HtmlUnit models the returned document."

See: http://htmlunit.sourceforge.net/

You might also want to check out XmlUnit, which allows you to perform XPath assertions on even poorly marked-up HTML (3.2). XhtmlUnit is a wrapper around XmlUnit to provide convenient methods for testing - you guessed it - XHTML documents.

HtmlUnit and JWebUnit would seem to come under the category of WebTester to me - MarcusBaker