The library’s own tests are integrated in HtmlUnit’s build and they now all (2) pass, no matter if we simulate Firefox 2, Firefox 3, Internet Explorer 6 or Internet Explorer 7. This time, it was not so complicated to reach 100% support: fix a bug in Rhino, implement a dummy support for the filters property on HTML elements when simulating IE, handle detached nodes for offsetParent, and fix a few things in computing CSS properties.
I believe that we’re on the right way and that we’ll soon be able to announce full support for other well known libraries.
(1) I suppose here that the library’s own tests are representative for the library usage.
(2) In fact we run only the tests files that pass in a “real” browser and therefore have to ignore 3 files.