def METHOD_NAME(self):
    # No types yet
    self.assertEqual(self.signal.types.count(), 0)
    self.assertIsNone(self.signal.type_assignment)
    self.signal.type_assignment = Type.objects.create(_signal=self.signal, name=Type.SIGNAL)  # Een melding
    self.signal.save()
    # Refresh the signal from the database
    self.signal.refresh_from_db()
    self.assertEqual(self.signal.types.count(), 1)
    self.assertEqual(self.signal.types.first().name, Type.SIGNAL)
    self.assertIsNone(self.signal.types.first().created_by)
    self.assertEqual(self.signal.type_assignment.name, Type.SIGNAL)
    self.assertIsNone(self.signal.type_assignment.created_by)