public function testGetLabelForUriReturnsEmptyStringLabelNotFound()
 {
     $graph = new ExtendedGraph();
     $label = "Wuthering Heights";
     $s1 = 'http://example.com/resource';
     $rdfType = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type';
     $graph->add_resource_triple($s1, $rdfType, 'http://xmlns.com/foaf/0.1/Person');
     $graph->add_literal_triple($s1, 'http://www.w3.org/2000/01/rdf-schema#label', $label);
     ExtendedGraph::initProperties(array('labelProperties' => array('http://www.w3.org/2000/01/rdf-schema#label2')));
     $this->assertEquals($graph->get_label_for_uri($s1), '');
 }