I cannot express myself better than Cgreen’s guide made by Baker, Nilsson and Freitas. There, you’ll find how to install Cgreen and how to get started with it. They show how to build and use test suites, how to mock C functions, and how to write assertion in BDD (Behavior-Driven Development) fashion. They take you on a ride to learn all the features of the framework while coding a kata that you can redo while you read.
Here’s a glimpse of how the framework is used. Enjoy!