Add code coverage for UpDownBase.UpDownBaseAccessibleObject

[MelonWang1]

Related #13442

Proposed changes

• Add unit test file: UpDownBase.UpDownBaseAccessibleObjectTests.cs for public methods of the UpDownBase.UpDownBaseAccessibleObject.cs.cs

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.

Project coverage is 76.59994%. Comparing base (8484b55) to head (050055d).
Report is 8 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13498         +/-   ##
===================================================
+ Coverage   76.59415%   76.59994%   +0.00579%     
===================================================
  Files           3230        3231          +1     
  Lines         639165      639182         +17     
  Branches       47297       47297                 
===================================================
+ Hits          489563      489613         +50     
+ Misses        146025      145995         -30     
+ Partials        3577        3574          -3     

Flag	Coverage Δ
Debug	76.59994% <82.35294%> (+0.00579%)	⬆️
integration	18.79551% <ø> (+0.01259%)	⬆️
production	51.00835% <ø> (+0.01256%)	⬆️
test	97.40338% <82.35294%> (-0.00074%)	⬇️
unit	48.41351% <ø> (+0.01221%)	⬆️

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Pull Request Overview

This PR adds unit tests to improve code coverage for the UpDownBase.UpDownBaseAccessibleObject class by verifying its GetChild and GetChildCount behavior.

• Introduces a new test file for UpDownBase.UpDownBaseAccessibleObject
• Covers valid and invalid index cases for GetChild
• Verifies the child count via GetChildCount

[ricardobossan]

Thank you!