This notebooks shows how a warning and an error is raised when there is no title in the first cell.

from nbproject import header, meta, publish
import pytest

header()

id	aK1IQUYIQsMs
version	0
time_init	2022-06-08 14:42
time_run	2024-10-16 16:26
pypackage_store	nbproject==0.0.7+2.g8521e30
pypackage_live	nbproject==0.10.4 pytest==8.3.3

meta.live.title  # returns None

publish() == "no-title"

✗ No title! Update & save your notebook with a title '# My title' in the first cell.

True