while 0 is less than 3, 0 means 'not in leaderboard'. So don't send a…

… Notification is somone is in the 0th rank in social engagement

lms/djangoapps/social_engagement/engagement.py

@@ -207,6 +207,12 @@ def handle_progress_post_save_signal(sender, instance, **kwargs):
             get_aggregate_exclusion_user_ids(instance.course_id)
         )['position']
 
+        if leaderboard_rank == 0:
+            # quick escape when user is not in the leaderboard
+            # which means rank = 0. Trouble is 0 < 3, so unfortunately
+            # the semantics around 0 don't match the logic below
+            return
+
         # logic for Notification trigger is when a user enters into the Leaderboard
         leaderboard_size = getattr(settings, 'LEADERBOARD_SIZE', 3)
         presave_leaderboard_rank = instance.presave_leaderboard_rank if instance.presave_leaderboard_rank else sys.maxint

lms/djangoapps/social_engagement/tests/test_engagement.py

@@ -383,3 +383,39 @@ def test_closed_course(self):
             # shouldn't be anything in there because course is closed
             leaderboard = StudentSocialEngagementScore.generate_leaderboard(course2.id)
             self.assertEqual(len(leaderboard), 2)
+
+    def test_no_score(self):
+        """
+        Run the engagement calculation for a user in a course who has no score
+        """
+
+        self.assertEqual(get_notifications_count_for_user(self.user.id), 0)
+
+        with patch('social_engagement.engagement._get_user_social_stats') as mock_func:
+            mock_func.return_value = {
+                'num_threads': 0,
+                'num_comments': 0,
+                'num_replies': 0,
+                'num_upvotes': 0,
+                'num_thread_followers': 0,
+                'num_comments_generated': 0,
+            }
+
+            update_user_engagement_score(self.course.id, self.user.id)
+
+            leaderboard_position = StudentSocialEngagementScore.get_user_leaderboard_position(
+                self.course.id,
+                self.user.id
+            )
+
+            self.assertEqual(
+                leaderboard_position['score'],
+                0
+            )
+
+            self.assertEqual(
+                leaderboard_position['position'],
+                0
+            )
+
+            self.assertEqual(get_notifications_count_for_user(self.user.id), 0)