C Automated Testing System (CATS) and its associated test runner (Catsrunner) implement a unit testing framework that provides developers of C-based systems, including embedded systems, the capability to use the popular test driven development approach. CATS supports embedded cross-platform development by working in conjunction with hardware abstraction layers. CATS also comes with a thin wrapper around arm-elf-gdb's host/target communication functions. A reference implementation for the ARM-7 CPU core is provided.