Added unit tests for filterResponses and isUsingResponsesToSelf

[hberehan]

Fixes #

Outline of Solution

[github-actions]

Hi @hberehan, thank you for your interest in contributing to TEAMMATES!
However, your PR does not appear to follow our contribution guidelines:

• Title must start with the issue number the PR is fixing in square brackets, e.g. [#<issue-number>]
• Description must reference the issue number the PR is fixing, e.g. Fixes #<issue-number> (or Part of #<issue-number> if the PR does not address the issue fully)

Please address the above before we proceed to review your PR.

[cedricongjh]

hi @hberehan, do fix the linting issues before we proceed to review this PR, you can test it locally via npm run lint before pushing it to github