NET-12: Add .NET 6 testing framework for HomeController migration

[devin-ai-integration]

Summary

Establishes a .NET 6 testing framework under a new netcore/ directory, alongside the existing MVC5/.NET Framework 4.5.1 solution at the repo root. Nothing in the legacy tree is modified.

Contents of netcore/:

• SampleWebApp.NetCore.sln tying together four new projects.
• src/SampleWebApp/ — an ASP.NET Core 6 port of HomeController (Index / About / Contact / Internals / CodeView) and a rewritten cross-platform InternalsInfo model. The model now goes through a new IInternalsInfoProvider abstraction (registered as a singleton in Program.cs) so counters can be mocked in tests.
• tests/SampleWebApp.UnitTests/ — xUnit + Moq + FluentAssertions. 13 tests covering every HomeController action and every InternalsInfo code path. Coverlet (msbuild + collector) reports 100% line / branch / method on HomeController.cs and InternalsInfo.cs.
• tests/SampleWebApp.IntegrationTests/ — 10 tests using WebApplicationFactory<Program>. Hits /, /Home, /Home/Index|About|Contact|Internals|CodeView over HTTP, asserts 200 OK + text/html, plus content checks on About/Internals and a 404 case. Program.cs exposes a public partial class Program { } hook so the factory can bind.
• tests/SampleWebApp.PerformanceTests/ — BenchmarkDotNet project with HomeControllerBenchmarks (one bench per action, Index as Baseline) and InternalsInfoBenchmarks. Run on demand; not wired into CI.
• coverlet.runsettings excluding Program.cs and *.cshtml from coverage.
• docs/testing.md + docs/test-results.md + netcore/README.md.

.gitignore updated to exclude coverage.*.xml, TestResults/, BenchmarkDotNet.Artifacts/.

Review & Testing Checklist for Human

This PR is yellow risk — the tests all pass locally but there are a few deliberate interpretation calls that deserve a second look.

• Scope call: NET-1 isn't done yet. NET-12's stated dependency is "HomeController migration completion," but the legacy SampleWebApp/Controllers/HomeController.cs is still MVC5. To have something testable I wrote a minimal .NET 6 port of the controller as part of this PR. Confirm this is acceptable, or split it out into a separate NET-1 PR and keep only the test harness here.
• Behavioral drift in the migrated InternalsInfo. The original uses Windows-only PerformanceCounter("Memory", "Available MBytes"); I replaced it with GC.GetGCMemoryInfo() (available memory derived from TotalAvailableMemoryBytes - MemoryLoadBytes). HeapMemoryUsedKbytes also switched from GC.GetTotalMemory(forceFullCollection: true) to false. These values are no longer numerically equivalent to the MVC5 output — confirm this is an acceptable tradeoff for cross-platform.
• Views are placeholders, not real migrations. About/Contact/Internals/CodeView .cshtml files are minimal stubs so the integration tests have something to render. The real content will need to come from whoever completes NET-1.
• Performance acceptance criterion ("equal or better performance") is only partially addressed. I established a benchmark harness and baseline, but there's no automated comparison against the legacy MVC5 numbers (they can't run on Linux). Confirm this scope of "performance tests" is what the team expected.
• Big auto-scaffolded wwwroot/. dotnet new mvc pulled in bootstrap/jquery/jquery-validation assets. They're not hand-edited but they inflate the diff significantly.

Suggested test plan

dotnet build netcore/SampleWebApp.NetCore.sln -c Release
dotnet test  netcore/tests/SampleWebApp.UnitTests/SampleWebApp.UnitTests.csproj -c Release \
  /p:CollectCoverage=true /p:CoverletOutputFormat=cobertura \
  '/p:Include="[SampleWebApp]*"' \
  '/p:ExcludeByFile="**/Program.cs,**/*.cshtml,**/obj/**/*.cs"'
dotnet test  netcore/tests/SampleWebApp.IntegrationTests/SampleWebApp.IntegrationTests.csproj -c Release
dotnet run  --project netcore/tests/SampleWebApp.PerformanceTests -c Release -- --list flat

Also worth spot-checking coverage.cobertura.xml: Controllers/HomeController.cs and Models/InternalsInfo.cs should both be at line-rate="1".

Notes

• No changes to the legacy MVC5 solution at the repo root.
• The legacy repo does not have CI configured on GitHub (no .github/workflows), so CI checks may not run on this PR.
• Closes / addresses NET-12.

Link to Devin session: https://app.devin.ai/sessions/c28119099a4e4047a4af9236a226e3e3

[devin-ai-integration]

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