This chapter from <a href="http://www.informit.com/store/more-agile-testing-learning-journeys-for-the-whole-9780321967053?w_ptgrevartcl=Using+Models+to+Help+Plan+Tests+in+Agile+Projects_2253544">More Agile Testing: Learning Journeys for the Whole Team</a> looks at some foundations of agile test planning and how they are evolving.