`api/core.py` test coverage

[nitinawari]

Proposed change

Your PR description goes here.

• close #991
• Added test coveraege for api/core.py
• 

Type of change

• [ ] New core framework functionality
• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] Code refactoring without any functionality changes
• [ ] New or existing module/payload change
• [ ] Localization improvement
• [ ] Dependency upgrade
• [ ] Documentation improvement
• [x] test coverage

Checklist

• [x] I've followed the contributing guidelines
• [x] I've run make pre-commit, it didn't generate any changes
• [x] I've run make test, all tests passed locally

[nitinawari]

@securestep9 @arkid15r I started writing test cases for each file to reach the maximum test coverage. For this file, I have achieved 100% test coverage. I need a review of the code quality and syntax style so that I can apply the same approach to the other tests.