public function test__serializer()
{
$esd = new EntitiesDescriptor();
$esd->addItem(new EntityDescriptor('ed1'));
$esd->addItem(new EntityDescriptor('ed2'));
$esd2 = new EntitiesDescriptor();
$esd2->addItem(new EntityDescriptor('ed3'));
$esd->addItem($esd2);
$ctx = new SerializationContext();
$esd->serialize($ctx->getDocument(), $ctx);
$xpath = new \DOMXPath($ctx->getDocument());
$xpath->registerNamespace('md', SamlConstants::NS_METADATA);
$this->assertEquals(1, $xpath->query('/md:EntitiesDescriptor')->length);
$this->assertEquals(2, $xpath->query('/md:EntitiesDescriptor/md:EntityDescriptor')->length);
$this->assertEquals(1, $xpath->query('/md:EntitiesDescriptor/md:EntityDescriptor[@entityID="ed1"]')->length);
$this->assertEquals(1, $xpath->query('/md:EntitiesDescriptor/md:EntityDescriptor[@entityID="ed2"]')->length);
$this->assertEquals(1, $xpath->query('/md:EntitiesDescriptor/md:EntitiesDescriptor')->length);
$this->assertEquals(1, $xpath->query('/md:EntitiesDescriptor/md:EntitiesDescriptor/md:EntityDescriptor[@entityID="ed3"]')->length);
}