Add code coverage for DesignerUtils

[Zheng-Li01]

Related https://github.com/dotnet/winforms/issues/10773

Proposed changes Add unit test file: DesignerUtilsTests.cs for public methods & properties of the DesignerUtils.cs

Note: working on another PR for the remaining test case

Microsoft Reviewers: Open in CodeFlow

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.58686%. Comparing base (71a8e95) to head (39a5a37). Report is 132 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13435         +/-   ##
===================================================
- Coverage   76.60371%   76.58686%   -0.01686%     
===================================================
  Files           3230        3253         +23     
  Lines         639097      641110       +2013     
  Branches       47289       47442        +153     
===================================================
+ Hits          489572      491006       +1434     
- Misses        145953      146450        +497     
- Partials        3572        3654         +82     

Flag	Coverage Δ
Debug	76.58686% <100.00000%> (-0.01686%)	:arrow_down:
integration	18.85583% <ø> (+0.06775%)	:arrow_up:
production	51.01200% <ø> (+0.00097%)	:arrow_up:
test	97.41258% <100.00000%> (+0.00847%)	:arrow_up:
unit	48.45871% <ø> (+0.03964%)	:arrow_up:

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[ricardobossan]

~~All LGTM, except that the CI fails no matter how many times I attempt to re-run failed checks. What do you think @LeafShi1 @Epica3055 ?~~

Nevermind. The issues were addressed.