One of the main differences between traditional lifecycles and agile lifecycles is the idea of very short iterations, each iteration resulting in working software that delivers features of value to business stakeholders. At the beginning of the project, there is often an inception period where the high-level goals of the project are defined and testing is planned in a high-level. This is followed by a sequence of iterations, each about one to four weeks in duration. In the beginning of each iteration, the detailed planning (including testing) for the iteration is performed. A small subset of the high level goals are specified as user stories with detailed acceptance criteria (i.e., the features to be built and their test conditions, respectively), then these features are developed, integrated with the system, and tested. These iterations are highly dynamic, with development, integration, and testing activities taking place throughout each iteration, with considerable parallelism and overlap. Testing activities are done all the time (i.e. daily), not just as a final activity of the iteration.
The text above is a sample from the upcoming Agile Tester Add-On that will be released in early 2014. Please note that Agile Tester Add-On is on alpha phase, which means that its content may change. Visit www.istqb.org to get latest information.