Which testing type focuses on verifying that the system functions fulfill user and task objectives?

Suitability testing is specifically designed to evaluate how well a system meets the needs of its users and whether it fulfills the intended tasks and objectives. This type of testing assesses the alignment of the software's functionality with user expectations, ensuring it is appropriate for its intended purpose. Through this process, the testing team can gather feedback from actual users to determine if the system satisfies predefined requirements and user demands.

This focus on user-centered evaluation distinguishes suitability testing from the other options. For instance, regressive testing primarily concerns itself with ensuring that new changes or defects introduced do not affect existing functionalities negatively, rather than verifying task fulfillment. Exploratory testing emphasizes ad-hoc investigation and exploration without predetermined tests, and while it can inform about suitability, it doesn't specifically target user objective fulfillment. Performance testing, on the other hand, is concerned with the responsiveness and stability of a system under varying conditions and loads, rather than directly verifying that it meets user expectations and task objectives.