Navigating for XP Projects

In Extreme Programming Explained and Planning Extreme Programming, Kent Beck compares XP to driving a car: you have to watch the road and make continual corrections to get to your destination.

Who is driving this car? What keeps the team from getting lost or making a wrong turn? Who makes them stop and ask directions? Any member of the team can perform this role, but the tester is a natural. The tester is suitably equipped to act as the navigator, reading the acceptance test "maps," interpreting the customer's requests, watching for signposts in the form of acceptance test results, and letting everyone know how the journey is progressing. Like the XP coach, the tester has a level of independent objectivity; the tester is a coach for the team with respect to testing and quality.

Mastering XP practices, like learning to drive, isn't always a smooth process. Lisa's friend Melody was "taught" to drive by her dad. His teaching technique consisted of burying his nose in a newspaper. He didn't notice that whenever she made a left turn, she turned into the left lane of the new street, directly into oncoming traffic. Since he didn't mention her left turns, Melody believed this was the correct way to drive. She found out differently the first time she drove with her mom, who reacted dramatically to her first left turn. Testers needn't be dramatic, but they can help make sure the team obeys the rules of the road and arrives safely at its destination.

An old truism says that when everyone is responsible, nobody is responsible. Everyone is responsible for quality in an Extreme Programming project, but it sure helps to have one or two team members whose primary focus is quality.