final IdentifierMap map = create(identifiers);
assertNull(map.put(IdentifierSpace.HREF, "myHREF"));
assertEquals("Shall contain the entry we added.", "myHREF", map.get(IdentifierSpace.HREF));
// Check the XLink object
final XLink link = map.getSpecialized(IdentifierSpace.XLINK);
assertEquals("Added href shall be stored as XLink attribute.", "myHREF", String.valueOf(link.getHRef()));
assertEquals("Identifier list shall contain the XLink.", link.toString(), getSingleton(identifiers).getCode());
// Modidfy the XLink object directly
link.setHRef(URI.create("myNewHREF"));
assertEquals("Change in XLink shall be reflected in href.", "myNewHREF", map.get(IdentifierSpace.HREF));
}