model: Update index when marking message as read.

Modify tests.

Author: kaustubh-nair

tests/model/test_model.py

@@ -1239,6 +1239,8 @@ def test_update_read_status(self, mocker, model, event_op,
                                 flags_before, flags_after):
         model.index = dict(messages={msg_id: {'flags': flags_before}
                                      for msg_id in indexed_ids})
+        model.index['unread_msg_ids'] = set(event_message_ids)
+
         event = {
             'messages': event_message_ids,
             'type': 'update_message_flags',
@@ -1272,6 +1274,8 @@ def test_update_read_status(self, mocker, model, event_op,
         elif event_op == 'remove':
             set_count.assert_not_called()
 
+        assert len(model.index['unread_msg_ids']) == 0
+
     @pytest.mark.parametrize('narrow, event, called', [
         # Not in PM Narrow
         ([], {}, False),

zulipterminal/model.py

@@ -838,6 +838,7 @@ def update_message_flag_status(self, event: Event) -> None:
         if event['operation'] == 'add' and flag_to_change == 'read':
             set_count(list(message_ids_to_mark & indexed_message_ids),
                       self.controller, -1)
+            self.index['unread_msg_ids'].difference_update(message_ids_to_mark)
 
     def update_rendered_view(self, msg_id: int) -> None:
         # Update new content in the rendered view