'Regression for #16260: save_new should call form.save()'

def test_save_new_uses_form_save(self):

    class SaveTestForm(forms.ModelForm, ):
        def save(self, *args, **kwargs):
            self.instance.saved_by = 'custom    method'
            return super().save(*args, **kwargs)
    Formset = generic_inlineformset_factory(ForProxyModelModel, fields='__all__', form=SaveTestForm)
    instance = ProxyRelatedModel.objects.create()
    data = {'form-TOTAL_FORMS': '1', 'form-INITIAL_FORMS': '0', 'form-MAX_NUM_FORMS': '', 'form-0-title': 'foo'}
    formset = Formset(data, instance=instance, prefix='form')
    self.assertTrue(formset.is_valid())
    new_obj = formset.save()[0]
    self.assertEqual(new_obj.saved_by, 'custom    method')
