Add unit test for HtmlElementErrorEventArgs.cs file

[Philip-Wang01]

Related #13442

Proposed changes

• Add unit test file: HtmlElementErrorEventArgsTests.cs for HtmlElementErrorEventArgs.cs file.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.59906%. Comparing base (5821493) to head (983c341).
Report is 18 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                  @@
##                main      #13512          +/-   ##
====================================================
+ Coverage   62.21083%   76.59906%   +14.38822%     
====================================================
  Files           3213        3231          +18     
  Lines         638302      639188         +886     
  Branches       47201       47297          +96     
====================================================
+ Hits          397093      489612       +92519     
+ Misses        234153      146002       -88151     
+ Partials        7056        3574        -3482     

Flag	Coverage Δ
Debug	76.59906% <100.00000%> (+14.38822%)	⬆️
integration	18.79166% <ø> (+0.00288%)	⬆️
production	51.00486% <ø> (+32.21608%)	⬆️
test	97.40428% <100.00000%> (+0.00016%)	⬆️
unit	48.40374% <ø> (?)

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