Add code coverage for ButtonRenderer

[Zheng-Li01]

Related #13442

Proposed changes

Add unit test file:ButtonRendererTests.cs for public/protected methods/properties of the ButtonRenderer.cs

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.95215%. Comparing base (255288f) to head (aff6dec).
⚠️ Report is 22 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13745         +/-   ##
===================================================
+ Coverage   76.90736%   76.95215%   +0.04479%     
===================================================
  Files           3260        3265          +5     
  Lines         643088      643904        +816     
  Branches       47601       47638         +37     
===================================================
+ Hits          494582      495498        +916     
+ Misses        144843      144730        -113     
- Partials        3663        3676         +13     

Flag	Coverage Δ
Debug	76.95215% <100.00000%> (+0.04479%)	⬆️
integration	18.98897% <ø> (-0.01148%)	⬇️
production	51.67584% <ø> (+0.09919%)	⬆️
test	97.42200% <100.00000%> (+0.00047%)	⬆️
unit	49.08321% <ø> (+0.12921%)	⬆️

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[ricardobossan]

All LGTM!