Test | Convert DateTimeVariantTests to xunit

[mdaigle]

Parameterizes tests using shared test data. Expected exceptions are made explicit in test data. Logging and baseline file comparisons are replaced with assertions.
Each commit can be reviewed individually to see the logical progression of the conversion.

[Copilot]

Pull request overview

This PR refactors the manual DateTime/sql_variant coverage from a baseline-file-driven harness into xUnit ConditionalTheory test cases, and removes the legacy helper/baseline artifacts.

Changes:

• Replaced the single baseline-comparison test runner with multiple [MemberData]-driven theory tests for different API paths (simple params, TVPs, bulk copy, reader paths).
• Deleted the legacy DateTimeVariantTest.cs harness and the DateTimeVariant.bsl baseline file.
• Updated the ManualTests project file to stop compiling/copying the removed files.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/ParameterTest/DateTimeVariantTests.cs	Reworked DateTime variant testing into xUnit theory-based tests with shared runner/helpers.
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/ParameterTest/DateTimeVariantTest.cs	Removed legacy standalone test harness implementation.
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/ParameterTest/DateTimeVariant.bsl	Removed baseline output file previously used for comparison.
src/Microsoft.Data.SqlClient/tests/ManualTests/Microsoft.Data.SqlClient.ManualTests.csproj	Removed compile/content entries for the deleted harness and baseline file.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

[edwardneal]

We don't need to open the connection in advance; the RAII objects take responsibility for opening the connection (if necessary) before creating or dropping the database object. The example pattern below would work just as well:

using SqlConnection conn = new(DataTestUtility.TCPConnectionString);
using Table testTable = new(conn, "MyTable", "(Id INT, Name NVARCHAR(100))");
using StoredProcedure proc = new(conn, "MyProc", $"AS BEGIN SELECT * FROM {testTable.Name} END");

using SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = proc.Name;
cmd.CommandType = CommandType.StoredProcedure;
// ... objects are automatically dropped when the scope ends

[mdaigle]

I think I'll leave it just to try and keep things explicit. It's a bit harder to track down a connection failure inside a helper method.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.32%. Comparing base (fdbc56e) to head (9688288).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4196      +/-   ##
==========================================
- Coverage   65.97%   64.32%   -1.66%     
==========================================
  Files         276      270       -6     
  Lines       42994    65800   +22806     
==========================================
+ Hits        28366    42323   +13957     
- Misses      14628    23477    +8849     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	64.32% <ø> (?)

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[paulmedynski]

I must have missed the PR that added these RAII objects.

One thing I'd like fixed (in this PR) is to ensure that the Dispose() methods never throw. As-is, a failure in one Dispose() will kill the test and inhibit other RAII objects from attempting their cleanup.