Fix typing tests

tests/rest/client/test_sync.py

@@ -282,22 +282,33 @@ def test_sync_backwards_typing(self) -> None:
         self.assertEqual(200, channel.code)
         next_batch = channel.json_body["next_batch"]
 
-        # This should time out! But it does not, because our stream token is
-        # ahead, and therefore it's saying the typing (that we've actually
-        # already seen) is new, since it's got a token above our new, now-reset
-        # stream token.
-        channel = self.make_request("GET", sync_url % (access_token, next_batch))
-        self.assertEqual(200, channel.code)
-        next_batch = channel.json_body["next_batch"]
-
         # Clear the typing information, so that it doesn't think everything is
-        # in the future.
+        # in the future. This happens automatically when the typing stream
+        # resets.
         typing._reset()
 
-        # Now it SHOULD fail as it never completes!
+        # Nothing new, so we time out.
         with self.assertRaises(TimedOutException):
             self.make_request("GET", sync_url % (access_token, next_batch))
 
+        # Sync and start typing again.
+        sync_channel = self.make_request(
+            "GET", sync_url % (access_token, next_batch), await_result=False
+        )
+        self.assertFalse(sync_channel.is_finished())
+
+        channel = self.make_request(
+            "PUT",
+            typing_url % (room, other_user_id, other_access_token),
+            b'{"typing": true, "timeout": 30000}',
+        )
+        self.assertEqual(200, channel.code)
+
+        # Sync should now return.
+        sync_channel.await_result()
+        self.assertEqual(200, sync_channel.code)
+        next_batch = sync_channel.json_body["next_batch"]
+
 
 class SyncKnockTestCase(KnockingStrippedStateEventHelperMixin):
     servlets = [