What is CppUTest. CppUTest is a C /C++ based unit xUnit test framework for unit testing and for test-driving your code. It is written in C++ but is used in C and C++ projects and frequently used in embedded systems but it works for any C/C++ project. CppUTest’s core design principles are: Simple in design and simple in use. Portable to old and new platforms. Build with Test-driven Development for