Which of the following testing types would primarily focus on only the output based on input?

The focus on output based on input makes black box testing the appropriate choice. In this testing approach, the internal workings of the application are not considered; instead, emphasis is placed solely on the outcomes generated from specific inputs. Testers do not need to understand how the system processes the inputs or the inner logic; instead, they verify that the inputs yield the expected outputs.

Black box testing is particularly effective for validating functional requirements and ensuring that the software behaves as intended from the user's perspective. By utilizing predefined input values, testers can ascertain whether the application responds correctly, aligning with the specifications without the need to inspect the underlying code or architecture. This method is widely adopted in various testing phases, including system testing and acceptance testing.

In contrast, other testing types, such as exploratory testing, involve an element of investigation and learning about the software by exploring its features without predefined test cases. Performance testing focuses on how well the software performs under various conditions, examining metrics like speed and stability. Alpha testing is conducted by developers in a controlled environment to identify bugs before releasing the software to a broader audience. These approaches involve more than just input-output validation, reiterating why black box testing is the right answer when considering merely the output resulting from given inputs.