Discover test projects in build pipelines

[angularsen]

Summary

• Discover *.Tests.csproj files instead of maintaining test project arrays.
• Evaluate each project's TargetFrameworks/TargetFramework with MSBuild and select only projects supporting the requested runtime.
• Share the same discovery function between the primary net10.0 test pipeline and the net48 compatibility workflow.
• Preserve separate test execution and coverage reports per project.

Motivation

PR #1692 added isolated test projects and exposed two independent hardcoded lists that could drift: first the net48 workflow omitted the projects, then the primary coverage pipeline did. Test discovery is an independent build-pipeline improvement and ensures future test projects are included automatically when they follow the existing naming convention and declare the target framework.

Validation

• Verified discovery returns all four current test projects for both net10.0 and net48.
• Verified discovery under PowerShell 7 and Windows PowerShell 5.1, which is used by build.bat.
• dotnet build UnitsNet.slnx --configuration Release --no-restore
• Start-Tests -SkipCoverage: 46,441 passed, 20 skipped across all four net10.0 test projects.
• The net48 discovery path selected all four projects and completed the first three locally; the full compatibility run is left to CI because the main net48 suite exceeded the local command window.

[claude]

Review

This is a build-tooling-only change (Build/build-functions.psm1, .github/workflows/net48-compatibility.yml) — no quantity/unit JSON, generated code, or public API changes, so there's nothing to check against the units/quantities criteria and no breaking changes.

What it does well

• Replaces two independently-maintained hardcoded project lists (the exact drift bug called out in the motivation, from Allow configuring global default quantities #1692) with a single Get-TestProjects discovery function shared by both the primary and net48 pipelines.
• Adds if ($testProjects.Count -eq 0) { throw ... } guards that didn't exist before — a good defensive addition so a discovery regression fails loudly instead of silently skipping all tests.
• Sort-Object FullName keeps discovery output deterministic across OS/filesystem enumeration order.
• Correctly accounts for the Condition="$([MSBuild]::IsOSPlatform('Windows'))" net48 addition in the test csproj files — net48 discovery only works on the Windows runner, which matches where net48-compatibility.yml actually runs (runs-on: windows-latest).

Minor nits (non-blocking)

• Build/build-functions.psm1:50: @($properties.Properties.TargetFrameworks -split ';') + $properties.Properties.TargetFramework doesn't trim whitespace after splitting. If a future <TargetFrameworks>net10.0; net48</TargetFrameworks> (space after ;) is ever added, -contains 'net48' would silently fail to match due to the leading space. Consider ... | ForEach-Object { $_.Trim() } to make this robust against that formatting variant.
• Same line: when a project only declares TargetFrameworks (no singular TargetFramework, the common case here), $properties.Properties.TargetFramework is empty/$null and still gets appended to the array. Harmless today since it never matches -Framework, but + @($properties.Properties.TargetFramework) | Where-Object { $_ } would keep the array purely meaningful values.
• Get-ChildItem -Path $root -Recurse -Filter "*.Tests.csproj" walks the entire repo tree (including .git, Artifacts, bin/obj) on every invocation. Not a correctness issue today with only 4 test projects, but worth keeping in mind if the repo grows — could scope to known source directories or add -Exclude/depth limits later.
• Each discovered project incurs its own dotnet msbuild -getProperty process spin-up. Fine at this scale (4 projects), but something to watch if the test-project count grows significantly.

Test coverage: Reasonable for a CI script change — author validated manually (discovery returns all 4 projects for both TFMs, PS 7/5.1, full net10 run, partial net48 run) per the PR description. No automated test for Get-TestProjects itself, but that's a normal tradeoff for build tooling and CI will exercise the real path on merge.

Overall: solid, well-scoped DRY fix for the exact problem it says it's solving. No blocking issues found.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96%. Comparing base (670ba36) to head (ed572ed).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #1693    +/-   ##
=======================================
- Coverage      96%     96%    -1%     
=======================================
  Files         455     457     +2     
  Lines       29540   30150   +610     
=======================================
+ Hits        28502   29086   +584     
- Misses       1038    1064    +26     

Flag	Coverage Δ
net48	96% <ø> (?)

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