Where release planning is a widening activity, iteration planning is more of a narrowing-down activity.
Scary as it is to race ahead without artifacts like requirements documents, the simplicity of stories and availability of the customer makes speeding safe.
Iteration planning is
Selecting the set of stories to be implemented in iteration
Breaking down the implementation of each story into a set of tasks
Estimating the effort required to accomplish each task
The tester's primary responsibility during iteration planning is helping the team think of all the tasks necessary to finish the story, especially those related to
Development infrastructure
Release packaging
Production environment
Test infrastructure
Acceptance testing
The tester also has the responsibility to help foster understanding between the development team and the customer and to strive for accuracy in task estimates.
