Sonar is an application for integrating output from several static and test analysis tools into a comprehensive overview of the software's quality.
Unfortunately, most of those analysis tools (PDM, FindBugs, etc.) do not support Groovy and, by extension, Grails.
We've found tools called CodeNarc and GMetrics which perform some of the analysis, but not test coverage, and we're working on a Sonar plugin to import the CodeNarc output. As I said, though, this is incomplete.
Does anyone know of a better set of complexity/rules-based static analysis tools that can handle Groovy, as well as a Grails test coverage metric? Of course, one with a Sonar plugin for reading in the output would be best.