function testTrackByReference()
 {
     $result = Postmaster_Tracking::track('1ZW470V80310800043');
     $this->assertTrue($result instanceof Postmaster_Tracking);
     $resultArray = $result->__toArray();
     $this->assertArrayHasKey('status', $resultArray);
     $this->assertArrayHasKey('history', $resultArray);
     $this->assertNotEmpty($result->history);
     $this->assertTrue($result->history[0] instanceof Postmaster_TrackingHistory);
 }