Which of the following tests focuses on the functionality of individual components?

The unit test is designed to focus on the functionality of individual components or pieces of code, such as functions, methods, or classes, in isolation from the rest of the program. This type of testing ensures that each component operates correctly on its own, which helps in identifying issues early in the development process. By confirming that each unit performs as intended, developers can build confidence in the stability and correctness of the code before moving on to testing interactions between components.

Other testing types, while important, serve different purposes. System tests evaluate the entire system as a whole, including how all components work together, while integration tests specifically check the interactions between different integrated units. Acceptance tests are conducted to determine whether a system meets the specified requirements and are often performed from the perspective of the end user.