What is the difference between an use case and test case ?

A use case captures business and user requirements related to system functions—that is, how the users interact with the system. The goal of a use case is to help the development team understand precisely what the users will expect the system to do.

A use case describes all the possible paths through a given user/system interaction, including the basic path and any alternative or exception paths. The basic (or “happy”) path is the one that meets the user’s needs. “Alternative paths” are additional paths that are acceptable but aren’t the most common, frequent, or desirable. “Exception paths” are those that fail to meet the user’s needs because of errors like missing information or invalid data. A single use case may describe many different paths.

Test cases are used to validate that the requirements have been met. The quality assurance analyst will probably want to test the system thoroughly by setting up an individual test case for each path described in a use case.

At a minimum, they would set up separate test cases for the “happy path,” each alternative path, and each exception path.