Extend unit testing

We are currently using a pdf view to check for changes of MR's.

However, not every test case should be included in the demo, as it is more a user guide.

A dedicated testing (automatic) infrastructure should exist.

https://tex.stackexchange.com/questions/12067/whats-the-folk-lore-on-automatic-testing-of-tex-programming

https://tex.stackexchange.com/questions/67192/using-qstest-to-implement-unit-tests

Edited by Leonard Fisser