public function testIsPropertySet()
{
$objectState = new ObjectState();
$value = isset($objectState->notDefined);
$this->assertEquals(false, $value);
$value = isset($objectState->id);
$this->assertEquals(true, $value);
$objectStateGroup = new ObjectStateGroup();
$value = isset($objectStateGroup->notDefined);
$this->assertEquals(false, $value);
$value = isset($objectStateGroup->id);
$this->assertEquals(true, $value);
}