Alpha and beta testing are forms of

Explanation

Alpha testing is carried out by the customer at the developer's site with the developer looking on; beta testing is carried out by real end users at their own sites, with faults reported back to the developer. Both exist to decide whether the delivered software is acceptable to the customer, so both are stages of acceptance testing (validation testing). White-box testing needs knowledge of internal code structure, which neither uses; black-box is a test-design technique rather than a level of testing; and system testing is performed by the development organisation before the product ever reaches the customer.