public function testExtensionAttributes()
 {
     $extensionAttributes = $this->visibility->extensionAttributes;
     $extensionAttributes['foo1'] = array('name' => 'foo1', 'value' => 'bar');
     $extensionAttributes['foo2'] = array('name' => 'foo2', 'value' => 'rab');
     $this->visibility->extensionAttributes = $extensionAttributes;
     $this->assertEquals('bar', $this->visibility->extensionAttributes['foo1']['value']);
     $this->assertEquals('rab', $this->visibility->extensionAttributes['foo2']['value']);
     $visibilityXml = $this->visibility->saveXML();
     $newVisibility = new Zend_Gdata_Extension_Visibility();
     $newVisibility->transferFromXML($visibilityXml);
     $this->assertEquals('bar', $newVisibility->extensionAttributes['foo1']['value']);
     $this->assertEquals('rab', $newVisibility->extensionAttributes['foo2']['value']);
 }