"Unit test" specs

[uliska]

files in the unit-tests directories are intended to be compiled during the (non-existing) automated test suite. They are intended to test cases that don't need to be included in the usage-examples but may be relevant to test in order to detect breaking changes.

These files should have a general format.

Blocks #26

[Cecca]

I think that this issue should not be related to the documentation part of the project, but should rather belong to its own project

[uliska]

Probably you're right. Still I'd like to keep an eye on it as it complements the "usage examples"