I would go so far to say that one can’t be successful in any of these practices without some degree of test automation in place. In my experience, teams often have more developers than testers, in which case the developers need to take responsibility for most of the team’s testing and automation efforts. The responsibility for testing lies within an Agile team. Test activities are planned and controlled in the same way as all other activities within a Sprint. Each member of the team can (and should) carry out testing tasks according to his or her own individual skills.