public void test_UnitDefinition_parent_NULL()
        {
            SBMLDocument   d = new SBMLDocument();
            Model          m = d.createModel();
            UnitDefinition c = m.createUnitDefinition();
            Unit           u = c.createUnit();

            assertTrue(u.getAncestorOfType(libsbml.SBML_UNIT_DEFINITION) == c);
            UnitDefinition c1 = c.clone();

            d = null;
            assertTrue(c1.getAncestorOfType(libsbml.SBML_MODEL) == null);
            assertTrue(c1.getParentSBMLObject() == null);
            assertEquals(c1.getSBMLDocument(), null);
            assertTrue(c1.getUnit(0).getAncestorOfType(libsbml.SBML_UNIT_DEFINITION) == c1);
            assertTrue(c1.getUnit(0).getParentSBMLObject() != null);
            assertEquals(c1.getUnit(0).getSBMLDocument(), null);
            c1 = null;
        }