Unittest for pinned post

[nidhin29]

This change included the Unittest for pinned post

Issue Number: #2161

Fixed #2161

Did you add tests for your changes?

Yes

Summary

It is unittest for pinned_post.

Does this PR introduce a breaking change?

No, this does not introduce any major changes to the codebase.

Have you read the contributing guide?

Yes, i have followed the guidelines.

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[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (b548497) 76.43% compared to head (456dffa) 79.86%.
Report is 35 commits behind head on develop.

❗ Current head 456dffa differs from pull request most recent head 758f878. Consider uploading reports for the commit 758f878 to get more accurate results

Files	Patch %	Lines
lib/widgets/pinned_post.dart	90.90%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2171      +/-   ##
===========================================
+ Coverage    76.43%   79.86%   +3.42%     
===========================================
  Files          152      152              
  Lines         7438     7458      +20     
===========================================
+ Hits          5685     5956     +271     
+ Misses        1753     1502     -251     

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[noman2002]

Write tests for missing lines, the coverage is dropping significantly.