Acceptance testing (AT) is a testing process that is applied to ascertain whether the software products under development have met the requirements specified by agreement, e.g., contract. It helps validate, typically through functional testing, that the software items fulfill the requirements and specifications appropriate for the life cycle of the software product, AT can be performed in phases, and either on the interim or final software products for both new and modified software systems. It is conducted under controlled conditions using documented procedures to generate, acquire, and record data that accurately measure the software product against predefined criteria for functionality, performance, interface quality, and identified quality attributes (e.g., safety, security, reliability, interoperability). This activity may involve all or some of the following: instrumentation, test software, simulation software, and/or special test equipment; and includes the evaluation of the acquired data to verify compliance with specified performance requirements.