[test] Re-add item-separator serialization tests
[test] Re-add item-separator serialization tests

eXist-db/exist,eXist-db/exist,eXist-db/exist,lcahlander/exist,lcahlander/exist,adamretter/exist,dizzzz/exist,dizzzz/exist,dizzzz/exist,dizzzz/exist,lcahlander/exist,adamretter/exist,adamretter/exist,adamretter/exist,adamretter/exist,dizzzz/exist,lcahlander/exist,eXist-db/exist,dizzzz/exist,lcahlander/exist,eXist-db/exist,eXist-db/exist,adamretter/exist,lcahlander/exist