Increasing code coverage and cover negative/success scenarios in unit tests.

[enraiha0307]

Hi team,
I was studying this project for contribution, and I observed that some files still have coverage of < 50%.
I would like to write unit tests that help cover the missing statements and error scenarios.
I believe this would benefit the project as well as help me understand the project code flow better and in turn, I will be able to identify new things to contribute.

[qweeah]

@enraiha0307 thanks for volunteering! Looking forward to your PR.

[shizhMSFT]

Adding this issue to the future milestone as it is a long-term issue to be resolved.