This commit extends TestCreateObjMetadata. The test function does not
just verify CreateObjMetadata, but also uses ParseObjMetadata to verify
back and forth between both functions. I left specific testing of
ParseObjMetadata in place, because there might be edge cases, that
should be tested on its own.
I'm aware, that the TestCreateObjMetadata now tests two things, but I
think it makes life of maintainers and new contributors far easier.
E.g. the change I introduced in #193 would have been catched by tests,
rather than someone with a mental model of all of the code.