This document discusses testing of controls during an audit. It provides details on the types of audit procedures used for testing controls, including physical examination, confirmation, documentation, observation, accuracy, analytical evidence, and client inquiry. The reliability of different types of evidence is also discussed, with physical evidence and confirmation considered the most reliable, followed by external documentation and tests of accuracy. Guidelines are provided around the extent of testing controls, including reliance on prior audits and testing controls related to significant risks in the current year. Examples are also given around sample sizes used for testing controls.