def METHOD_NAME(self):
    parent_category = ParentCategoryFactory.create(slug='wonen')
    parent_db_cnt = Category.objects.filter(parent__isnull=True).count()
    child_db_cnt = Category.objects.filter(parent__isnull=False).count()
    out = StringIO()
    err = StringIO()
    call_command('dummy_categories', parent_slug=parent_category.slug, children_to_create=5, stdout=out, stderr=err)
    self.assertEqual(Category.objects.filter(parent__isnull=True).count(), parent_db_cnt)
    self.assertEqual(Category.objects.filter(parent__isnull=False).count(), child_db_cnt + 5)