Test on one tablet and one phone. App: With user X Navigate to a user discussion on messages with user Y. Website or other app: enter as user Y and navigate to the same user discussion with user X. User X: scroll up the discussion. User Y send some messages (recommended 5 or more). User X: check there's a new badge at bottom right that indicates the new messages count. User X: click on the button and check it scrolls to the first recently received message and updates the number. (If bottom is not reached, click again until the button disappears). Repeat steps 3 to 5. User X: Scroll manually and check the count is updated when scrolling, and it disappears at the bottom. User X: Now scroll to to the top and load previous messages. Check the new messages badge does not change.