Which testing type primarily focuses on the system's behavior and experience from a user perspective?

User acceptance testing (UAT) is designed specifically to evaluate a system from the end user's perspective, ensuring that the software meets their needs and expectations. This type of testing involves real users who assess the functionality, usability, and overall experience of the application in a controlled environment that simulates real-world usage.

During UAT, users focus on verifying that the system behaves as intended in scenarios that are representative of actual usage. They check whether the system is intuitive, user-friendly, and whether it fulfills the requirements specified by stakeholders. This is crucial for achieving user satisfaction and ensuring that the final product aligns with business goals and user requirements.

In contrast, the other testing types serve different purposes: unit testing focuses on individual components for correctness, integration testing assesses how various components work together, and regression testing ensures that changes have not adversely affected existing functionality. Therefore, UAT stands out as the testing type that emphasizes the user experience and system behavior from an end-user viewpoint.