Added unit tests for most of the pubsub classes that did not have any

[tishun]

Closes #2805

Make sure that:

• [x ] You have read the contribution guidelines.
• [x ] You have created a feature request first to discuss your contribution intent. Please reference the feature request ticket number in the pull request.
• [x ] You use the code formatters provided here and have them applied to your changes. Don’t submit any formatting related changes.
• [x ] You submit test cases (unit or integration tests) that back your changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.62%. Comparing base (43843bf) to head (347078e).
Report is 241 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2808      +/-   ##
============================================
- Coverage     78.71%   77.62%   -1.09%     
- Complexity     6786     7190     +404     
============================================
  Files           508      537      +29     
  Lines         22765    24376    +1611     
  Branches       2446     2603     +157     
============================================
+ Hits          17919    18922    +1003     
- Misses         3717     4253     +536     
- Partials       1129     1201      +72     

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