feat: migrate Domain.Tests to xUnit v3 (#163)

[mpaulosky]

Summary

Migrates Domain.Tests from xUnit v2 (2.9.3) to xUnit v3 (3.2.2) as the pilot project for Sprint 7.

Working as Gimli (Tester) 🪓

Closes #163

Changes

File	Change
Directory.Packages.props	Added xunit.v3 3.2.2 alongside existing xunit 2.9.3 (other projects unaffected)
tests/Domain.Tests/Domain.Tests.csproj	Replaced xunit → xunit.v3 package reference; added xunit.runner.json as content
tests/Domain.Tests/xunit.runner.json	New: v3 runner config (parallel execution, method display, no diagnostics)

Zero source changes required — the 42 test files use simple [Fact]/[Theory] patterns with no ITestOutputHelper, IAsyncLifetime, or collection fixtures. The Xunit namespace is unchanged in v3.

Test Results

Suite	Result
Domain.Tests (xUnit v3)	✅ 42/42 pass
Architecture.Tests	✅ 11/11 pass
Web.Tests	✅ 105/105 pass
Web.Tests.Bunit	✅ 61/61 pass

Notes

• xunit.runner.visualstudio 3.1.5 was already in place and is v3-compatible — no change needed.
• NuGet change from [Sprint 7] chore(test): add xunit.v3 to Directory.Packages.props alongside xunit v2 #162 was folded into this PR since [Sprint 7] chore(test): add xunit.v3 to Directory.Packages.props alongside xunit v2 #162 had no commits beyond the sprint base.

[github-actions]

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[Copilot]

Pull request overview

Migrates tests/Domain.Tests from xUnit v2 to xUnit v3 as a pilot for the broader multi-sprint rollout, while keeping the rest of the test projects on xUnit v2.

Changes:

• Added xunit.v3 (3.2.2) to central package versions alongside existing xunit v2.
• Switched tests/Domain.Tests to reference xunit.v3 and added an xUnit runner config file to output.
• Introduced tests/Domain.Tests/xunit.runner.json with parallelization and method display settings.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
Directory.Packages.props	Adds centrally-managed version for xunit.v3 to enable per-project migration.
tests/Domain.Tests/Domain.Tests.csproj	Switches the test framework package to xunit.v3 and copies runner config to output.
tests/Domain.Tests/xunit.runner.json	Adds xUnit runner configuration for Domain.Tests.

[Copilot]

The migration to xUnit v3 in this project is missing the <OutputType>Exe</OutputType> change required by issue #163 (and recommended by the xUnit v3 migration guide for the new test host). Add OutputType=Exe in the main <PropertyGroup> for this project so the PR meets the acceptance criteria and avoids runner/adapter surprises.

[Copilot]

xunit.runner.json is already included by the SDK as a None item; adding it as Content Include=... can lead to the file being present in multiple item lists and makes this project inconsistent with the existing pattern in Web.Tests.Integration (which uses <None Update=...>). Prefer updating the existing None item (or removing the default inclusion) and set CopyToOutputDirectory there.

Suggested change

	<Content Include="xunit.runner.json" CopyToOutputDirectory="PreserveNewest"/>
	<None Update="xunit.runner.json" CopyToOutputDirectory="PreserveNewest"/>

[github-actions]

Test Results Summary

209 tests  ±0   209 ✅ ±0   14s ⏱️ ±0s
  5 suites ±0     0 💤 ±0 
  5 files   ±0     0 ❌ ±0 

Results for commit 791c75d. ± Comparison against base commit e7035b1.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (sprint/7-xunit-v3-pilot@18e668f). Learn more about missing BASE report.

Additional details and impacted files

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##             sprint/7-xunit-v3-pilot     #170   +/-   ##
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  Coverage                           ?   72.53%           
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  Files                              ?       43           
  Lines                              ?      721           
  Branches                           ?      112           
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  Hits                               ?      523           
  Misses                             ?      149           
  Partials                           ?       49           

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