Fix xunit.v3 test discovery and code coverage in CI (dotnet test / VSTest incompatibility)

[Copilot]

xunit.v3 runs via the Microsoft Testing Platform (MTP) in-process runner; dotnet test defaults to VSTest discovery, which cannot see MTP-hosted tests — producing "No test is available" and, consequently, 0% coverage from an empty run.

CDT.Tests.csproj

Two MSBuild properties wire up the MTP pipeline end-to-end:

<!-- Routes dotnet test / MSBuild from the VSTest target to the MTP target -->
<TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
<!-- Activates the MTP runner inside the test host -->
<UseMicrosoftTestingPlatformRunner>true</UseMicrosoftTestingPlatformRunner>

Both are required — the first fixes the MSBuild/dotnet test side, the second fixes the runner side. Either one alone is insufficient.

coverlet.collector was also replaced with coverlet.msbuild. The collector variant hooks into VSTest's IDataCollector API which MTP bypasses entirely, leaving the coverage XML file unwritten (hence ReportGenerator failing with "no matching files"). coverlet.msbuild rewrites IL at build time and is runner-agnostic.

.github/workflows/ci-cd.yml

The Test steps were updated to use coverlet.msbuild MSBuild properties instead of the VSTest-only --collect:"XPlat Code Coverage" argument:

/p:CollectCoverage=true
/p:CoverletOutputFormat=cobertura
/p:CoverletOutput=${{ github.workspace }}/coverage/coverage.cobertura.xml

The ReportGenerator input path was updated to match the workspace-absolute output location.

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[MichaConrad]

@copilot Thats great, now

• create more sophisticated examples in the readme
• test them to make sure they actually work
• Look at the original c++ repos' readme
  • mention the original repo and
  • add any information to ours which might be very important (don't copy all the things, just if you find something note worthy)
  • and mention to look at hte soruce repo for documentation and all that because we'll not port all that over
  • Give proper credit

[Copilot]

@copilot Thats great, now

• create more sophisticated examples in the readme
  ...

Done in da1e0d4. Here's what changed:

README improvements:

• Added a proper "What is CDT?" section explaining constrained vs. conforming DT
• Pre/post-conditions section (no duplicate vertices, CCW winding) — ported from upstream
• 6 sophisticated, fully working examples: convex hull, constrained DT with bounded domain, auto-detected holes (even–odd depth rule), conforming DT, duplicate vertex removal + edge remapping, and resolving intersecting constraint edges
• Credited the original C++ repo and its contributors with the MPL-2.0 attribution template, and linked to the upstream docs for full algorithm/API documentation since we won't port all of that

Tests:

• Added ReadmeExamplesTests.cs with 7 tests (one per example) that validate every code snippet in the README compiles and produces the expected output — all passing.

[MichaConrad]

@copilot Looks like the build is failing becasue our VIZ app must target windows only

can you fix that?

  Determining projects to restore...
Error: /usr/share/dotnet/sdk/10.0.103/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.FrameworkReferenceResolution.targets(120,5): error NETSDK1100: To build a project targeting Windows on this operating system, set the EnableWindowsTargeting property to true. [/home/runner/work/CDT.NET/CDT.NET/viz/CDT.Viz/CDT.Viz.csproj]
Error: Process completed with exit code 1.

[MichaConrad]

Great!

@copilot

Now, why is the CI/CD reporting 0% code coverage at the end though?
I see that the report is generated and attached to the pipeline output

How can that be with 990 tests?

[MichaConrad]

@copilot

Now both builds fail in the step to report on code coverage with

Installing ReportGenerator global tool (https://www.nuget.org/packages/dotnet-reportgenerator-globaltool)
/usr/share/dotnet/dotnet tool install dotnet-reportgenerator-globaltool --tool-path reportgeneratortool --version 5.5.1 --ignore-failed-sources
You can invoke the tool using the following command: reportgenerator
Tool 'dotnet-reportgenerator-globaltool' (version '5.5.1') was successfully installed.
Successfully installed ReportGenerator global tool
Executing ReportGenerator
/home/runner/work/CDT.NET/CDT.NET/reportgeneratortool/reportgenerator -reports:./coverage/**/coverage.cobertura.xml -targetdir:coveragereport -reporttypes:MarkdownSummaryGithub -sourcedirs: -historydir: -plugins: -assemblyfilters:+* -classfilters:+* -filefilters:+* -riskhotspotassemblyfilters:+* -riskhotspotclassfilters:+* -verbosity:Info -title: -tag:7_22275618183 -license:
2026-02-22T10:47:16: The report file pattern './coverage/**/coverage.cobertura.xml' found no matching files.
2026-02-22T10:47:16: No report files specified.
Error: Failed to execute ReportGenerator global tool

[Copilot]

@copilot

Now both builds fail in the step to report on code coverage with
...

Fixed in d5b7afe. Root cause: coverlet.collector uses VSTest's data-collection callbacks, which MTP silently ignores — so the XML file was never written, leaving ReportGenerator nothing to find.

Switched to coverlet.msbuild (which rewrites IL at build time, independent of the test runner) and updated the Test steps to pass /p:CollectCoverage=true /p:CoverletOutputFormat=cobertura /p:CoverletOutput=... instead of --collect:"XPlat Code Coverage". Verified locally: 997 tests pass and coverage.cobertura.xml is generated with 85.86% line coverage.

[github-actions]

Summary

Summary

Generated on:	2/22/2026 - 10:55:45 AM
Coverage date:	2/22/2026 - 10:55:41 AM
Parser:	Cobertura
Assemblies:	1
Classes:	17
Files:	7
Line coverage:	85.8% (1227 of 1429)
Covered lines:	1227
Uncovered lines:	202
Coverable lines:	1429
Total lines:	3230
Branch coverage:	80.4% (602 of 748)
Covered branches:	602
Total branches:	748
Method coverage:	Feature is only available for sponsors
Tag:	8_22275718617

Coverage

CDT.Core - 85.8%

Name	Line	Branch
CDT.Core	85.8%	80.4%
CDT.Box2d`1	73.3%	100%
CDT.CdtUtils	68%	50%
CDT.CovariantReadOnlyDictionary`3	18.1%	50%
CDT.DictionaryExtensions	100%	100%
CDT.DuplicatesInfo	100%
CDT.DuplicateVertexException	66.6%
CDT.Edge	75%	66.6%
CDT.IntersectingConstraintsException	0%
CDT.KdTree`1	72.5%	65%
CDT.LayerDepth	0%
CDT.Predicates	79.5%	91.8%
CDT.TopologyVerifier	77.2%	63.8%
CDT.Triangle	69.5%	71.4%
CDT.TriangleUtils	94.7%	87%
CDT.Triangulation`1	94.6%	84.2%
CDT.TriangulationException	100%
CDT.V2d`1	44.4%	25%