Which of the following describes all components of a system that provide information and controls for the user?

The user interface is the correct choice as it encompasses all the components of a system that allow the user to receive information and exert control over the system’s functionality. This includes elements such as buttons, menus, forms, and any visual cues that enable interaction. The user interface is crucial in ensuring that users can navigate the system effectively and access the functionalities they need.

A test case, while important in the context of testing, specifically refers to a set of conditions or variables under which a tester determines whether a system or part of a system is working as intended. It does not encompass the broader concept of user interaction.

Validation relates to ensuring that the product meets the requirements and fulfills its intended purpose but does not specifically address the components through which the user interacts with those requirements.

Agile methodology describes a framework or set of practices for developing software incrementally and iteratively but does not pertain to the components that provide direct interaction and information to the user.

Thus, the user interface is the most accurate term to describe the components that facilitate user interaction and provide necessary controls and information.