The unit tests for hms_artisan.data_storage are, at this point, all concerned with testing the JSONFileDataStore class. Because of what that class actually does, the typical patterns for unit testing apply poorly, if at all. It has no properties to test, and the one class attribute that can be tested (_file_store_dir) is overridden by derived classes.
It's probably worth asserting that the default attribute is what's expected, though, since if it doesn't default to None, that could cause failures in derived classes and instances of those classes:
def test_file_store_dir(self):
self.assertEqual(
JSONFileDataObject._file_store_dir, None,
'JSONFileDataObject._file_store_dir is expected to provide '
'a None default value that must be overridden by derived '
'classes, but it...