[Core][Testing] Add unit tests for most of the components

[gdt050579]

Possible candidates: gtest, catch2 catch = https://github.com/catchorg/Catch2/ gtest = https://github.com/google/googletest

A couple of things that are of interest:

1. to be quickly able to see if all tests have passed or not
2. to be able to run only a couple of tests from the command line
3. to be able to easily debug if a test fails

A comparation research between those two frameworks (or others) is needed.