Add test cases for idGenerator utils

[rahulrk-dev]

Description

Please include a brief summary of the change and include the relevant issue(s).

Closes #197

What change does this PR introduce?

Please select the relevant option(s).

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to docs/code comments)
• Unit test

What is the proposed approach?

Please give a short overview/explanation on the approach taken to resolve the issue(s).

Checklist:

• The commit message follows our adopted guidelines
• Testing has been done for the change(s) added (for bug fixes/features)
• Relevant comments/docs have been added/updated (for bug fixes/features)

[tjtanjin]

LGTM! 😊

[rahulrk-dev]

Thanks @tjtanjin