Fix back link on ‘sent’ page in tour

If the user wants to go back from here they need to be sent back to the
start of entering the placeholders, because we won’t have their previous
personalisation in the session still

I think the back link on this page was introduced by accident. But it’s
good to still have it on this page, because it keeps consistency with
the previous pages.

app/main/views/notifications.py

@@ -101,8 +101,13 @@ def view_notification(service_id, notification_id):
     show_cancel_button = notification['notification_type'] == 'letter' and \
         letter_can_be_cancelled(notification['status'], notification_created)
 
-    if request.args.get('help') == '0':
-        back_link = None
+    if get_help_argument():
+        back_link = url_for(
+            'main.send_test',
+            service_id=current_service.id,
+            template_id=template.id,
+            help='2',
+        )
     elif request.args.get('from_job'):
         back_link = url_for(
             'main.view_job',

tests/app/main/views/test_notifications.py

@@ -125,12 +125,22 @@ def test_notification_status_page_respects_redaction(
         partial(url_for, 'main.view_job', job_id='job_id'),
     ),
     (
-        {'help': '0'},
-        None,
+        {'help': '0'},  # not a valid help step
+        partial(url_for, 'main.view_notifications', message_type='sms', status='sending,delivered,failed'),
     ),
     (
         {'help': '0', 'from_job': 'job_id'},
-        None,
+        partial(url_for, 'main.view_job', job_id='job_id'),
+    ),
+    (
+        {'help': '1'},
+        partial(
+            url_for,
+            'main.send_test',
+            service_id=SERVICE_ONE_ID,
+            template_id='5407f4db-51c7-4150-8758-35412d42186a',
+            help='2'
+        ),
     ),
 ])
 def test_notification_status_shows_expected_back_link(