  
      @isolate_apps('signals')
      def test_not_loaded_model(self):
          signals.post_init.connect(
              self.receiver, sender='signals.Created', weak=False
          )
  
          try:
              class Created(models.Model):
                  pass
 
</s> remove     @isolate_apps('signals')
    def test_not_loaded_model(self):
 </s> add     @isolate_apps('signals', kwarg_name='apps')
    def test_not_loaded_model(self, apps): </s> remove         msg = "Specified sender must either be a model or a model name of the 'app_label.ModelName' form."
 </s> add         msg = "Invalid model reference 'invalid'. String model references must be of the form 'app_label.ModelName'."
            self.receiver, sender='signals.Created', weak=False, apps=apps
  
      @isolate_apps('signals')
      def test_not_loaded_model(self):
          signals.post_init.connect(
            self.receiver, sender='signals.Created', weak=False, apps=apps
          )
  
          try:
              class Created(models.Model):
                  pass
keep keep keep keep replace keep keep keep keep keep
 Fixed #26421 -- Refactored ModelSignal to use Apps.lazy_model_operation() 
tests/signals/tests.py