Which type of testing verifies that software functions according to specified requirements?

Functional testing is designed to verify that software functions as specified in its requirements. This type of testing is centered around assessing the software's functionalities against defined requirements to ensure that it behaves as expected in various scenarios.

During functional testing, testers evaluate user interfaces, APIs, databases, security, and other functionalities by providing appropriate input and examining the output against the requirements. The primary objective is to confirm that each feature performs its intended function without any discrepancies.

Unit testing assesses individual components for correctness, while integration testing evaluates how well those components work together, often focusing more on interactions than on functional requirements. Performance testing, on the other hand, is concerned with how the system performs under a certain load, including its responsiveness and stability, rather than whether it meets specified functional requirements. Therefore, functional testing is the clear choice in this context as it directly aligns with verifying compliance to requirements.