In software development, ensuring that an application works as intended is paramount. This process, known as functional testing, verifies that the software performs according to specified requirements. However, focusing solely on functionality can overlook critical aspects that affect user experience, system performance, and overall software quality. Enter non-functional testing—a comprehensive approach to evaluating performance, security, usability, and reliability. Mastering non-functional testing is essential for delivering superior software that meets and exceeds user expectations.