A recent post about in-memory database unit testing by Mike Bosch reminded me of a presentation I wrote but never published about developer testing and how to achive 100% test coverage for nasty applications. High test coverage for most parts of an application is easy, for some parts it's difficult to do. The hard parts are Swing parts (which Jemmy can help with) and database parts (which hsql in-memory can help with). With the tips and tools in the presentation it's possible to reach 100% test coverage. But I conclude that most of the time 100% test coverage not needed.