Create app context switch test helper

[paulmedynski]

Description

This change adds a test helper to get/set app context switch values. The LocalAppContextSwitches class is internal and global, which makes it difficult to manipulate safely in the tests. The helper implements the RAII pattern, capturing the switch values on construction and restoring them on disposal. The helper also provides reflection-based access to the properties and fields of LocalAppContextSwitches so tests can manufacture the environment they need.

The new LocalAppContextSwitchesHelper class is needed by both the Functional and Manual tests, so I put it into a new sibling Common directory and reference it directly in the two test projects.

All existing tests that touched the app context switches have been updated.

Issues

Fixes #3370 .

Testing

Modified tests were run locally and are passing. CI will run full regression.

[Copilot]

Pull Request Overview

This PR introduces a new test helper—LocalAppContextSwitchesHelper—to safely capture and restore global app context switches using the RAII pattern. The changes update various test projects to utilize the helper instead of direct reflection-based switch manipulation, refactor the TdsParserStateObject to dispose of switch state correctly, and adjust some test inline data to match the new API.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/ManualTests/SQL/DataReaderTest/DataReaderTest.cs	Replaced direct switch handling with the helper to ensure proper restoration.
tests/ManualTests/Microsoft.Data.SqlClient.ManualTesting.Tests.csproj	Added compilation reference for the new helper.
tests/FunctionalTests/TdsParserStateObject.TestHarness.cs	Refactored to use a disposable helper instance and implemented IDisposable.
tests/FunctionalTests/SqlParameterTest.cs	Updated test inline data and usage of the helper for switch configuration.
tests/FunctionalTests/MultiplexerTests.cs	Converted state object instantiation to a using statement for proper disposal.
tests/FunctionalTests/Microsoft.Data.SqlClient.Tests.csproj	Included the helper compilation.
tests/FunctionalTests/LocalAppContextSwitchesTests.cs	Amended inline test data to cover new switch properties.
tests/Common/LocalAppContextSwitchesHelper.cs	Introduced the new helper class implementation.

Comments suppressed due to low confidence (2)

src/Microsoft.Data.SqlClient/tests/FunctionalTests/TdsParserStateObject.TestHarness.cs:161

• [nitpick] Consider renaming the 'LocalAppContextSwitches' field to clearly indicate it is an instance of the helper rather than the original static switch holder.

private SwitchesHelper LocalAppContextSwitches = new();

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlParameterTest.cs:1947

• The removal of test cases using null switch values changes the expected behavior. Please verify that omitting these cases is intentional and that the documentation and coverage adequately address the default switch behavior.

[InlineData(null, 7, null)]

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 6 lines in your changes missing coverage. Please review.

Project coverage is 67.67%. Comparing base (1eabf80) to head (db9609e).
Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
...icrosoft/Data/SqlClient/LocalAppContextSwitches.cs	77.77%	4 Missing ⚠️
.../netcore/src/Microsoft/Data/SqlClient/TdsParser.cs	0.00%	1 Missing ⚠️
...nt/netfx/src/Microsoft/Data/SqlClient/TdsParser.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3371      +/-   ##
==========================================
+ Coverage   64.47%   67.67%   +3.19%     
==========================================
  Files         298      299       +1     
  Lines       65525    65640     +115     
==========================================
+ Hits        42248    44419    +2171     
+ Misses      23277    21221    -2056     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	72.97% <71.42%> (+4.47%)	⬆️
netfx	65.43% <75.00%> (+0.06%)	⬆️

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[benrr101]

Good idea, good implementation, just a bunch of style stuff I want to make sure we get right.

[benrr101]

Much better, thank you for addressing the feedback 👍