def METHOD_NAME(self):
    req = Requirement()
    self.assertEqual(len(req.prerequisites), 0)
    req = Requirement(specification=TestSpecification(prerequisites={'andrew'}))
    self.assertEqual(len(req.prerequisites), 1)
    self.assertEqual(req.prerequisites, {'andrew'})
    req = Requirement(details=[Detail(specification=TestSpecification(prerequisites={'andrew'})),
                               Detail(specification=TestSpecification(prerequisites={'1980'}))])
    self.assertEqual(len(req.prerequisites), 2)
    self.assertEqual(req.prerequisites, {'andrew', '1980'})