Unit testing of the GUI is not the same as unit testing through the GUI. We are interested in the logic of the GUI rather than the placement and order of the GUI widgets on screen.
Testing the logic makes the tests less sensitive to changes in presentation but introduces the problem of JavaScript dependent features. AJAX is in the vogue so we wish to be able to do testing of that too without being forced to start a browser. There is some support for AJAX in Wicket that may be reached using the test framework that is part of Wicket. However, it is not straightforward to use and there are some pitfalls.
Here are three examples of avoiding those, one for each of the check box, drop down and radio group controls.
Each page has a form submit that takes you to the next page.
Read the source and read the pages. One would believe that the controls should be tested in a similar way, but no, they are very different from each other.