/** 
  * @covers WindowsAzure\Common\Internal\Atom\Feed::writeXml
  */
 public function testWriteXmlInvalidParameter()
 {
     // Setup
     $feed = new Feed();
     $this->setExpectedException(get_class(new \InvalidArgumentException()));
     // Test
     $actual = $feed->writeXml(null);
     // Assert
 }