Josh recently pointed me to this
very nice guide,
which contains a very in-depth explanation of all the mechanisms available to
JDK5 developres to troubleshoot and diagnose failures.  The document is 124
pages long, so I’m not sure if we should be happy or scared, but it’s a very
interesting read nevertheless.

A couple of TestNG links:

• 
  Thierry Janaudy’s article on TestNG at JavaWorld.
• JavaHispano published
  my
  interview (both in English and Spanish).

My Spanish has never been that good.