Added content on writing unit tests and mocks in C with AUM

[c8y3]

I have written a succinct introduction to unit tests in C with AUM (https://github.com/airbus-cyber/aum).
AUM is a C unit testing library which focuses on the easy definition of mocks.
I explain the reason for doing unit tests, the structure of a test, the notion of mocks and list some best practices. All the examples are written using the AUM API.

[pvalena]

Hello. It looks good!

However, I'd like it to look more Fedora-friendly, as this is aimed solely at Fedora users.

E.g. https://github.com/developer-portal/content/blob/master/tech/languages/c/gtk.md

• Starts with overview (we really aim at short quickstarts)
• Continues with dnf install (fedora-specific) .. could be replaced by COPR. f.e..
• Example (simple usage)
• References documentation.

Also, this could be possibly generalized- are there any other mocking libraries (just to list them for comparison)?