def METHOD_NAME(self, notify_on_new_thread_reply_mock):
    """posts merge sums mentions"""
    user = create_test_user("User1", "user1@example.com")
    other_user = create_test_user("User2", "user2@example.com")
    response = self.client.post(
        self.post_link, data={"post": "This is test response, @%s!" % user}
    )
    self.assertEqual(response.status_code, 200)
    post_a = self.user.post_set.order_by("id").last()
    self.assertEqual(post_a.mentions.count(), 1)
    self.assertEqual(list(post_a.mentions.all()), [user])
    # post second reply
    self.user.last_post_on = None
    self.user.save()
    response = self.client.post(
        self.post_link,
        data={"post": "This is test response, @%s and @%s!" % (user, other_user)},
    )
    self.assertEqual(response.status_code, 200)
    post_b = self.user.post_set.order_by("id").last()
    # merge posts and validate that post A has all mentions
    post_b.merge(post_a)
    self.assertEqual(post_a.mentions.count(), 2)
    self.assertEqual(list(post_a.mentions.order_by("id")), [user, other_user])