Port older tests in the new test system

[giomba]

Current status

Some source files contain a section which is normally not compiled unless CEDA_TEST is defined as a preprocessor macro.
This has the advantage of permitting access to some "private" structs of the module under test, but it is actually bad practice, and to be honest also "ugly".

Desiderata

Tests sources should be clearly separed into dedicated *_test.c files, and all the additional infrastructure to handle the CEDA_TEST macro removed.