Shun the Dark Side
Just as we had a caveat for testers on the potential of XP to solve quality assurance and testing problems, we also have one for XP teams on the potential of testers to help XP projects. The tester role we advocate in this book is not the traditional quality assurance/testing role. It follows a much more integrated, team-oriented approach and requires adapting one's skills and experience to function in an XP environment.
Just as you wouldn't want to be in the tester role on a team that claims to be XP but doesn't follow the practices (see "Wolves in Sheep's Clothing" in Chapter 1), you also wouldn't want to have a tester on your XP team who doesn't understand and buy into the methodology. A tester who views programmers as adversaries or doesn't believe in test automation or expects to spend more time planning than doing is likely to cling to techniques honed on traditional software projects. This will, in the best case, fail to help and, in the worst case, undermine the rest of the team's adherence to XP practices. Find a tester who understands and is committed to XP.