def METHOD_NAME(self):
    """Verifies subtopics appear on document listing page."""
    # Create a topic and product.
    p = ProductFactory()
    t = TopicFactory(product=p, visible=True)
    # Create a documents with the topic and product
    doc = DocumentFactory(products=[p], topics=[t])
    ApprovedRevisionFactory(document=doc)
    # GET the page and verify no subtopics yet.
    url = reverse("products.documents", args=[p.slug, t.slug])
    r = self.client.get(url, follow=True)
    self.assertEqual(200, r.status_code)
    pqdoc = pq(r.content)
    self.assertEqual(1, len(pqdoc(".subtopics>li")))
    # Create a subtopic, it still shouldn't show up because no
    # articles are assigned.
    subtopic = TopicFactory(parent=t, product=p, visible=True)
    r = self.client.get(url, follow=True)
    self.assertEqual(200, r.status_code)
    pqdoc = pq(r.content)
    self.assertEqual(1, len(pqdoc(".subtopics>li")))
    # Add a document to the subtopic, now it should appear.
    doc.topics.add(subtopic)
    r = self.client.get(url, follow=True)
    self.assertEqual(200, r.status_code)
    pqdoc = pq(r.content)
    self.assertEqual(2, len(pqdoc(".subtopics>li")))