The devil's in the wiring...
If you had a pile of 5000 perfectly made bricks, could you guarantee the resulting house wouldn't fall down?
Originally Posted by unkreativ
It's true that some parts of your system are only testable using integration tests (usually the edge bits like DAOs and views), but it's also worth testing the "glue" in the middle, to make sure that each component is passing the correct messages to its collaborators. The web tier is a rich source of such problems, e.g. a view containing a slightly different target URL to the one configured in the URL mapper.
"Now is the EJB of our discontent made glorious Spring"