Hi Rachel,
You need to create tests for your own plugins/modification or just test general moodle functionalities? We are running daily functional tests (Last Moodle 2.5 results: http://integration.moodle.org/job/5.-%20Run%20all%20behat%20features%20(MOODLE_25_STABLE)/lastCompletedBuild/testReport/(root)/)
If silk4net is a requirement for you I can not help with it, I have no idea.