@Test
public void testIllegalOccurrence() throws IOException, SchemaSyntaxException {

  OSLSchema schema = (OSLSchema) readSchema("in", "intocc.xml");
  TopicIF type = makeType("#something");
  TopicIF instance = builder.makeTopic();
  instance.addType(type);
  TopicIF occtype = makeType("#illegalocctype");
  OccurrenceIF occ = builder.makeOccurrence(instance, occtype, "This occurrence is internal, but of the wrong type.");
  validate(schema); // topic class is loose, so this is OK
}