          class Question(models.Model):
              pass
  
          class Answer(models.Model):
              question = models.ForeignKey(Question)
  
              class Meta:
                  order_with_respect_to = 'question'
  
          self.assertEqual(Answer.check(), [])
 
</s> remove             question = models.ForeignKey(Question)
 </s> add             question = models.ForeignKey(Question, models.CASCADE) </s> remove     employee = models.ForeignKey(Employee)
 </s> add     employee = models.ForeignKey(Employee, models.CASCADE) </s> remove     question = models.ForeignKey(Question, on_delete=models.PROTECT)
 </s> add     question = models.ForeignKey(Question, models.PROTECT) </s> remove             parent = models.ForeignKey(Parent)
 </s> add             parent = models.ForeignKey(Parent, models.CASCADE) </s> remove             content_type = models.ForeignKey(ContentType)
 </s> add             content_type = models.ForeignKey(ContentType, models.CASCADE)
            question = models.ForeignKey(Question, models.CASCADE)
          class Question(models.Model):
              pass
  
          class Answer(models.Model):
            question = models.ForeignKey(Question, models.CASCADE)
  
              class Meta:
                  order_with_respect_to = 'question'
  
          self.assertEqual(Answer.check(), [])
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/invalid_models_tests/test_models.py