This document discusses unit testing and test-driven development (TDD) in ABAP. It defines unit testing as a method to test individual units of code, such as methods and functions, to find bugs early. An xUnit framework provides automated testing with setup, test, and teardown methods. SAP's implementation is called ABAP Unit. TDD involves writing tests before code is written in a cycle of red, green, refactor to drive the development process. The document concludes with a code kata example to practice TDD with converting numbers to Roman numerals.