That my tests will not be equivalent is no big problem. In this case I am really unit testing the pages while mocking the backend. That allows me to also test anomalous behavior of the backend.
In addition, I am also doing unit integration testing with rendering wicket pages with an actual JPA backend with a relatively complete environment including transactions and JPA. So, overall my unit tests cover the functionality quite well. The trick I am doing now is storing the mock in a static variable of the test class and then creating a serializable proxy using LookupProxyFactory ( http://utils.wamblee.org/support/general/apidocs/org/wamblee/general/LookupProxyFactory.html) to lookup the mock dynamically. I guess this is screaming again for another test utility on top of mockito for creating serializable mocks (if I cannot solve it in wicket). Any suggestions on how to disable serialization in wicket tester?