An acceptance test procedure (ATP) is a type of testing that is used to ensure that a product meets the specific requirements of the customer or client. ATPs are often used in software development, but can also be used for hardware or other products. ATPs typically involve defining a set of acceptance criteria and then testing the product against those criteria. If the product meets all of the acceptance criteria, it is considered to be acceptable. ATPs can be used at various stages of development, but are often used at the end of the development process to ensure that the final product meets all requirements.