This presentation: http://www.cafeaulait.org/slides/sdbestpractices2006/legacy/
Testing legacy code: http://www-128.ibm.com/developerworks/java/library/j-legacytest.html
Working Effectively with Legacy Code
Michael Feathers
Prentice Hall, 2004
ISBN 0-131-17705-2
Cobertura: http://cobertura.sourceforge.net/
Measure test coverage with Cobertura: http://www.ibm.com/developerworks/java/library/j-cobertura/
Clover: http://www.cenqua.com/clover/
JUnitDoclet: http://www.junitdoclet.org/