Increase test coverage for shared.py to 100% #359

Job	Run time
unittest_matrix (macos-latest, 3.12)	1m 51s
unittest_matrix (ubuntu-latest, 3.12)	54s
black	16s
quantumespresso	26m 50s
arithmetic	2m 13s
unittest_matrix (ubuntu-latest, 3.11)	49s
pip_check	56s
nfdi4ing	7m 15s
documentation	45s
	41m 49s

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