The video4linux subsystem of the kernel is a very large API with many ioctls, settings, options and capabilities. This poses a problem both for the kernel developer and for the application developer. Since early this year major improvements have been made to both the v4l2-compliance utility for verifying drivers, and the virtual video drivers that applications can use as a reference input or output. This presentation will explain and demonstrate these tools and drivers and show how to use them to ensure your driver or application works correctly.