test suite for pyenzyme

[haeussma]

As recommended by @fbergmann, we should add a test suite for pyenzyme to rule out creation of faulty or invalid documents.

[JR-1991]

Sounds great! There is already a small test suite. We should think about which cases may be relevant to test for. Do you have some in mind already?

[fbergmann]

The best thing, would be to first come up with a set of validation rules we really care about. And from there implement the validation rules, and for that create systematically each mistake we can make.