Use case testing is a specification-based test technique that is based on the use cases or scenarios that describe how users interact with the system under test. Use case testing aims to find defects in the process flow or functionality of the system under test by verifying that it behaves as expected according to the use cases or scenarios. Use case testing does not require any knowledge of the data flow or structure of the system under test; it only focuses on what the system does rather than how it does it. Use case testing can be done by professional testers or real users, depending on the level and purpose of testing. Use case testing can also be designed by customers or end users, developers, testers, analysts, or anyone who has access to the use case specifications or user requirements. You can find more information about use case testing in [A Study Guide to the ISTQB Foundation Level 2018 Syllabus], Chapter 4, Section 4.2.