A procedure for testing the functionality of the infrastructure that has built up. And to ensure that the system is processed correctly. Meet the needs of users who have requested it.
As a step to test the functionality of the system infrastructure that has been built up and to make sure that the system is processed correctly. Meets the needs of the user who has requested.
As a step to test the operation of the system infrastructure that has been built up, and to make sure that there is a system for processing has been correct in accordance with the needs of the user that has been requested.