Canoo WebTest shines with excellent test coverage for both unit and functional testing as measured and visible under http://webtest.canoo.com/webtest/manual/buildOverview.html .
The comprehensive documentation can be found under http://webtest.canoo.com/webtest/manual/manualOverview.html . Interestingly, this documentation is constructed from the sources with every build that is triggered by the CruiseControl continuous integration as visible under http://webtest.canoo.com/buildservlet/BuildServlet .
Canoo WebTest was a pioneer project and one of the first open-source projects ever that embraced automatic builds, continuous integration, measuring test coverage and reaching close to 100% in this area.