In Agile the team normally consists of the BA, Developer, and Tester. It some organizations, the tester is responsible for manual, automated and performance testing activities. That is a lot of responsibility for one person but it does happen in small IT organizations. In larger organizations it gets a little more complicated. I have setup multiple testing departments and I create a shared services model for both automation and performance work. The tester works with those teams and identifies automation and performance testing efforts. I do require that if the test case is going to be automated, it needs to provide the right amount of detail so the automation team will be able to script it properly. I also like the manual tester to execute and pass the test case before it is automated. Input in terms of the stability of the code is also needed, otherwise you can burn a lot of hours having to constantly update changing automated scripts. The beauty of this model is it allows multiple Agile teams to leverage automation and performance skills. As more automation and performance testing is needed, those shared services team will grow creating a model that can scale.
The Agile teams don’t typically need dedicated resources for automation and performance testing, so hours are only used when needed. To keep in line with the Agile methodology, I have both my automation and performance teams create Sprints for the work that is needed so I can closely measure how things are going within a given timeline. Since the effort is shared across the team, they follow standard Agile principles and have their own series of meetings, demos, and retrospectives to ensure communication is flowing across the team. They also may participate in some of the meetings such as daily stand ups for the projects they are supporting.
I have adjusted this model a bit to fit the needs of each organization. It has worked well and I will continue to use it moving forward. The teams like the approach and it has helped to build stronger teams using this approach.