Agile testing is dynamic approach for testing. In this testing requirement is not stable, it keeps on changing according to customer.
Agile testing involves testing from customer perspective as early as possible, testing early often as code becomes available and stable enough from the module level testing or unit level testing. Testing the application in iteration is called sprint. If there is any further change in the requirements from client side then that requirement is covered under next Iteration 2 (Sprint 2).