Built-in self-test is a design methodology and technique where test logic is integrated directly into a system or circuit, enabling it to test itself autonomously. This academic concept investigates methods for generating test stimuli, analyzing responses, and detecting faults within a system using its own resources, reducing dependence on external testers. Its significance lies in enhancing system testability, reducing manufacturing and field testing costs, and improving the reliability and maintainability of complex electronic and digital systems throughout their lifecycle.