White-Box Testing is a software testing method that involves examining the internal structures or workings of an application. Testers have access to the source code and can design test cases based on the code's logic, algorithms, and control flow. This approach helps identify hidden errors and ensures that all code paths are tested. By using White-Box Testing, developers can improve code quality and optimize performance. It is particularly useful for unit testing, where individual components are tested in isolation. This method complements other testing types, such as Black-Box Testing, which focuses on the application's functionality without considering the internal code.