public function testSaveValidNewDocument()
{
// create document
$document = $this->getMock('\\Sokil\\Mongo\\Document', array('rules'), array($this->collection));
$document->expects($this->any())->method('rules')->will($this->returnValue(array(array('some-field-name', 'required'))));
$document->set('some-field-name', 'some-value')->save();
}