Add test coverage for CheckedListBox.CheckedItemCollection and CheckedIndexCollection

[Olina-Zhang]

Related #10453

Proposed changes

• Add unit tests for CheckedListBox.CheckedItemCollection to test its properties: SyncRoot, IsSynchronized, IsFixedSize, IsReadOnly
• Add unit tests for CheckedListBox.CheckedItemCollection to test its methods: Add, Clear, Insert, Remove, RemoveAt, Contains, IndexOf, CopyTo, GetEnumerator
• Update unit tests for CheckedListBox.CheckedIndexCollection to test its methods: Contains, IndexOf

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.29662%. Comparing base (f2118b8) to head (1c83a2a).
Report is 33 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #11384         +/-   ##
===================================================
+ Coverage   74.27372%   74.29662%   +0.02290%     
===================================================
  Files           3025        3027          +2     
  Lines         626861      627151        +290     
  Branches       46742       46761         +19     
===================================================
+ Hits          465593      465952        +359     
+ Misses        157926      157852         -74     
- Partials        3342        3347          +5     

Flag	Coverage Δ
Debug	74.29662% <100.00000%> (+0.02290%)	⬆️
integration	17.99717% <ø> (+0.00123%)	⬆️
production	47.03623% <ø> (+0.03453%)	⬆️
test	96.98767% <100.00000%> (-0.00649%)	⬇️
unit	44.01403% <ø> (+0.04294%)	⬆️

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[ricardobossan]

Other than small comment, LGTM.

[Tanya-Solyanik]

I would prefer to create controls for each test to ensure that we start with a clean control every time

[Tanya-Solyanik]

I see that test class is created before every test is run, but are we guaranteed that the constructor is executed on the STA thread? and that DIspose method is always called even if the test fals?

[Olina-Zhang]

We are following this reference: constructor and dispose pattern.
A TestInitialize like method does not exist in xunit, we have added an empty construct for its uniform operation.
As far as we know, when test cases are run in pipeline, they are randomly assigned to the machine each time and then executed by the vstester, one test case at a time. So, there will be no case of multiple test cases running at the same time.
Are we going to continue to write like this or are we going to use the original creating controls for each test?

[Tanya-Solyanik]

Thank you for the pointer to docs. My other concern was that winforms controls should be used from the same thread they are created on. But in your cases you are not calling CreateControl, only the constructor. So Disposable pattern looks fine.