[Feature]: Improve test converage to 90%

[bendichter]

What would you like to see added to MatNWB?

see title

Is your feature request related to a problem?

No response

What solution would you like?

see title

Do you have any interest in helping implement the feature?

Yes.

Code of Conduct

• [X] I agree to follow this project's Code of Conduct
• [X] Have you ensured this change was not already requested?