Which approach to testing focuses only on the application’s outputs without knowing the internal code?

The approach that focuses exclusively on an application's outputs without any knowledge of the internal code is known as blackbox testing. In this method, the tester interacts with the application by providing inputs and evaluating the resultant outputs, all while treating the application as a "black box." This approach is advantageous for assessing how the application behaves under various scenarios from an end user's perspective.

Typically, blackbox testing aims to ensure that the application meets its requirements and functions correctly in real-world situations, making it particularly useful for identifying user experience issues and functional deficiencies. Testers do not need to understand the underlying code, which emphasizes the testing of overall functionality, usability, and interactions with other systems or components.

Other testing methods, such as whitebox testing, involve examining the internal logic and structure of the code, while graybox testing combines both elements of whitebox and blackbox by having partial knowledge of the internal workings. Regression testing is a specific type of testing that focuses on verifying that previously developed and tested software still performs after a change, such as enhancements or bug fixes, rather than solely evaluating outputs.