My book PMD Applied has been out for a few months, but now I'm thinking of some things I'd like to be in there. Thus this announcement - I've just released a free supplemental chapter, "Better JUnit Tests With PMD"!
In this chapter I go through the PMD JUnit ruleset and show how you can use each rule to make your JUnit tests cleaner and more informative. Hopefully it will add more to the "PMD Applied" idea in that the chapter is devoted to, well, applying PMD to a particular domain - unit tests. You can download it in PDF format from the book's web site.