DUnitX is an open source Unit Test Framework, taking ideas from DUnit, NUnit and other test frameworks. It is designed to work with Delphi 2010 or later, it makes use of language/RTL features that are not available in older versions of Delphi.
DUnitX is included in the installer with recent versions of Rad Studio.
If you have questions about usage, best practices etc, ask them here. If you are experiencing an issue, or have feature requests, create an issue on GitHub. The bundled version may not always be the latest, so before you report bugs, try the version on Github first.