1. The testing carried out to verify that the acceptance criteria have been met. 2. A test that defines the business value each product backlog item must deliver. It may verify functional requirements or nonfunctional requirements such as performance or reliability. It is used to help guide development (Crispin and Gregory 2009). 3. Formal testing with respect to user needs, requirements, and business processes conducted to determine whether or not a system satisfies the acceptance criteria and to enable the user, customers, or other authorized entity to determine whether or not to accept the system (IEEE 610).