[christophwille]

Summary

Follow-up 3 from #1: the only tests were whole-project builds under tests/, which is how the TypeReferenceEquivalenceComparer bug (Cecil's GetElementType() returns the innermost type, so Nullable<bool>& compared equal to Nullable<byte>&) went unnoticed. This adds a small, fast unit test project for the weaver and runs it in CI.

ICSharpCode.ReferenceAssemblyAnnotator.Tests: xUnit v3 (xunit.v3.mtp-v2 4.0.3) on Microsoft Testing Platform, net10.0. The tests build tiny Cecil modules in memory (CecilBuilder), so they need no files and no real reference assemblies, and run in about a second.

What the tests cover (12 tests)

• Type comparer: by-ref, pointer and array types of Nullable<bool> vs Nullable<byte> (the regression); array rank; nested vs top-level types; generic arity; the same type shape from two different modules/assemblies compares equal (and has the same hash code).
• Method comparer: overloads that differ only in a by-ref generic argument are told apart.
• Program.AnnotateType (the full type walk, including FindMatchingMethod): the M(out bool?) / M(out byte?) case that used to throw in SingleOrDefault (MSB4018 for consumers); each overload now gets its own annotation.
• Program.Annotate: existing nullability attributes are replaced, not duplicated; unrelated attributes are kept.
• IsExcludedAnnotation: [DisallowNull] is not copied onto EqualityComparer<T>.GetHashCode / IEqualityComparer<T>.GetHashCode (theory over both types), while other annotations on the same parameter still are.

Changes

• New project ICSharpCode.ReferenceAssemblyAnnotator.Tests/, added to ReferenceAssemblyAnnotator.slnx. It inherits signing, nullable, StyleCop and warnings-as-errors from Directory.Build.props; IsPackable=false.
  • <PackageDownload Remove="Microsoft.NETCore.App.Ref" />: net10.0 isn't annotated, and the SDK adds its own targeting pack download when the pack isn't installed, so the repo-wide one would fail with NU1505 (same reason as the tests/ projects).
• Weaver (minimal): InternalsVisibleTo for the test assembly (same Key.snk, so the same public key as CecilBasedAnnotator), and Program.AnnotateType / Program.Annotate changed from private to internal. No behavior change.
• global.json: "test": { "runner": "Microsoft.Testing.Platform" }, so dotnet test runs in MTP mode.
• Workflow: new "Unit tests" step after "Build and pack" (dotnet test --project ICSharpCode.ReferenceAssemblyAnnotator.Tests -c Release --no-build). setup-dotnet now installs 10.0.x alongside 11.0.x, because the net10.0 test app needs the .NET 10 runtime and MTP apps don't roll forward across major versions.
• CLAUDE.md: the "There is no unit test project" line is replaced with how the unit tests work and how to run them.

Validation

• dotnet build ReferenceAssemblyAnnotator.slnx -c Release: 0 warnings, 0 errors.
• Unit tests: 12/12 pass.
• The tests catch the original bug: with the comparer's by-ref/pointer branches temporarily reverted to GetElementType(), 4 tests fail (ByReference_…, Pointer_…, MethodDefinition_…, AnnotateType_MatchesByRefGenericOverloads). The fix was restored afterwards.
• Only the annotator .nupkg is produced (the test project isn't packed).
• build/test.ps1 -Configuration Release -Engine dotnet: all 17 test builds pass. The msbuild engine wasn't run locally; CI covers it.

Not done, on purpose

• No end-to-end test through Program.Main (it needs real files and a resolvable core library); the tests/ projects already cover that path.
• Follow-up 2 from Port to .NET 10 SDK, rename to ICSharpCode.ReferenceAssemblyAnnotator, add GitHub Actions #1 (ambiguous matches abort the build) is unchanged; these tests make that change easier to do safely.

🤖 Generated with Claude Code