Added tests for truncate_titles() #983

Job	Run time
Lint Notebooks	8s
Black format	9s
Lint with flake8 for syntax+other error codes	7s
Type check	2m 57s
Test: Python 3.7 on ubuntu-latest	2m 54s
Test: Python 3.8 on ubuntu-latest	3m 54s
Test: Python 3.9 on ubuntu-latest	3m 42s
Test: Python 3.10 on ubuntu-latest	3m 51s
Test: Python 3.11 on ubuntu-latest	3m 25s
Test: Python 3.7 on macos-latest	1m 53s
Test: Python 3.8 on macos-latest	2m 50s
Test: Python 3.9 on macos-latest	3m 54s
Test: Python 3.10 on macos-latest	3m 32s
Test: Python 3.11 on macos-latest	2m 40s
Test: Python 3.7 on windows-latest	5m 38s
Test: Python 3.8 on windows-latest	4m 47s
Test: Python 3.9 on windows-latest	6m 12s
Test: Python 3.10 on windows-latest	5m 33s
Test: Python 3.11 on windows-latest	6m 58s
	1h 5m 4s

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