Unit test for the Linux kernel using Kunit

Update (2020-01-01): KUnit has merged in v5.5 merge window. From the writing of this post, it had some changes, so below content, especially the test setup and running will not work. Recommend you to refer to the official document in the kernel for detailed tutorial. It also has a python version dependency now, so you would encounter a problem with Ubuntu 16.04. Recommend you to use later Python or Ubuntu 18.