Canoo WebTest
Open source tool for automated web application testing
Cantata
Unit and integration testing tool for C and C++ on host and embedded targets
CMock
Mock and stub generator for unit testing C code
Ceedling
Build and unit test system for C projects based on Unity and CMock
Certify
Codeless automation of end-to-end business process tests for enterprise applications
cfix
xUnit unit testing framework for C/C++ on Windows, including kernel mode