@mock.patch.object(Site.objects, 'get_current')
    def test_watch_thread_then_reply(self, get_current):
        get_current.return_value.domain = 'testserver'
        u = UserFactory(username='jsocol')
        u_b = UserFactory(username='berkerpeksag')
        d = DocumentFactory(title='an article title')
        _t = ThreadFactory(title='Sticky Thread', document=d, is_sticky=True)
        t = self._toggle_watch_thread_as(u_b.username, _t, turn_on=True)
        self.client.login(username=u.username, password='testpass')
        post(self.client, 'wiki.discuss.reply', {'content': 'a post'},
             args=[t.document.slug, t.id])

        p = Post.objects.all().order_by('-id')[0]
        attrs_eq(mail.outbox[0], to=[u_b.email],
                 subject='Re: an article title - Sticky Thread')
        starts_with(mail.outbox[0].body, REPLY_EMAIL % {
            'user': u.profile.name,
            'document_slug': d.slug,
            'thread_id': t.id,
            'post_id': p.id,
        })

        self._toggle_watch_thread_as(u_b.username, _t, turn_on=False)
The event fires and sends emails when watching a thread.
dataset/ETHPy150Open mozilla/kitsune/kitsune/kbforums/tests/test_notifications.py/NotificationsTests.test_watch_thread_then_reply