Black box and white box testing are essential techniques in software testing, each focusing on different aspects of the application to ensure reliability and functionality. Black box testing evaluates the software's behavior from a user's perspective, focusing on inputs and outputs without knowledge of the internal code, making it ideal for validating user behavior, functionality, and performance in later stages of the software development lifecycle. Conversely, white box testing involves a thorough examination of the application's internal logic, code structure, and pathways, allowing testers to uncover hidden bugs and inefficiencies, making it more suitable for early-stage testing, such as unit and integration testing. Combining both methods provides a comprehensive view of software quality by addressing both the internal logic and the external user experience. Grey box testing, which blends elements of both approaches, is particularly useful for integration and security testing, where understanding both internal design and external behavior is crucial.