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	2024-05-06 22:20
pypackage_store	nbproject==0.0.7+2.g8521e30
pypackage_live	nbproject==0.10.1 pytest==8.2.0

meta.live.title  # returns None

publish() == "no-title"

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

True