'Deleting an instance of a concrete model should also delete objects
referencing its proxy subclass.'

def test_delete_concrete_parent(self):

    self.create_image()
    File.objects.all().delete()
    self.assertEqual(len(File.objects.all()), 0)
    self.assertEqual(len(Image.objects.all()), 0)
    self.assertEqual(len(FooFile.objects.all()), 0)
    self.assertEqual(len(FooImage.objects.all()), 0)
