So it seems that I have overseen one magic autotools switch which is still missing. Any help would be highly appreciated.
**Junk!** I simply forgot to install check on my machine (embarrassing). For anyone reading this: make sure you have check installed if you want to write unit tests. Otherwise you might get an error message like this:
If you execute the command ```./autogen.sh``` it will show if check is present/if unit tests can be created:
In case check is installed it will show ```Unit tests: yes```. If not, building tests via ```make check``` will fail.