Add unit test for LLM call_tool method

[aniketmaurya]

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

users will get a tested code as the LLM.call_tool method was not covered in test

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in GitHub issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81%. Comparing base (ed2bb48) to head (7edc731).
⚠️ Report is 90 commits behind head on main.

Additional details and impacted files

@@        Coverage Diff         @@
##           main   #21   +/-   ##
==================================
+ Coverage    73%   81%   +7%     
==================================
  Files         6     6           
  Lines       294   329   +35     
==================================
+ Hits        215   265   +50     
+ Misses       79    64   -15     

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