When testing a software module without knowing its internal structure or code, what specific testing technique is being applied?

The specific testing technique being applied is Black-Box Testing. Black-Box Testing is a method of software testing where the tester evaluates the functionality of a software module without any knowledge of its internal structure, design, or implementation details, such as the source code or how algorithms are constructed. The term 'black box' signifies that the module's internal workings are opaque to the tester, meaning they cannot be seen. The primary goal of this technique is to verify that the software meets its specified requirements and behaves as expected from an external user's perspective. Testers interact with the software by providing various inputs through its defined interfaces, such as a user interface or an API, and then observing and validating the corresponding outputs. This approach focuses solely on what the system does—its functionality and behavior—rather than how it achieves those results. For instance, when testing a calculator application, a tester would input numbers and mathematical operations, then check if the displayed result is correct, without needing to examine the code that performs the calculations.