Surge test is one of the EMC tests. It aims to simulate the effects of lightning on AC power supplies and any long cables.
IEC 61000-4-5 relates to the immunity requirements, test methods, and range of recommended test levels for equipment with regard to unidirectional surges caused by overvoltages from switching and lightning transients. Several test levels are defined which relate to different environment and installation conditions. These requirements are developed for and are applicable to electrical and electronic equipment.