test: migrate the tests from xUnit to TUnit

.github/dependabot.yml

@@ -23,9 +23,9 @@ updates:
       fallout:
         patterns:
           - "Fallout*"
-      xunit:
+      tunit:
         patterns:
-          - "xunit*"
+          - "TUnit*"
       aweXpect:
         patterns:
           - "aweXpect*"

AGENTS.md

@@ -4,8 +4,8 @@ Mockolate is a source-generated mocking library for .NET. Users write `IFoo.Crea
 
 ## SDK and Build
 
-- Use the SDK pinned in `global.json` (.NET 10, `rollForward: latestMinor`). Tests also run on .NET 8, and on .NET Framework 4.8 on Windows only.
-- Build from the root with `dotnet build Mockolate.slnx`. Shared settings live in the root `Directory.Build.props` (strong naming, `MinimumRoslynVersion`), `Source/Directory.Build.props` (target frameworks, warnings as errors, AOT and trimming flags) and `Tests/Directory.Build.props` (test frameworks, xUnit, aweXpect).
+- Use the SDK pinned in `global.json` (.NET 10, `rollForward: latestPatch`). Tests also run on .NET 8, and on .NET Framework 4.8 on Windows only.
+- Build from the root with `dotnet build Mockolate.slnx`. Shared settings live in the root `Directory.Build.props` (strong naming, `MinimumRoslynVersion`), `Source/Directory.Build.props` (target frameworks, warnings as errors, AOT and trimming flags) and `Tests/Directory.Build.props` (test frameworks, TUnit, aweXpect).
 - Package versions belong only in `Directory.Packages.props`. `VersionOverride` is used only to pin Roslyn packages to `$(MinimumRoslynVersion)`.
 
 ## Design Goals
@@ -22,7 +22,7 @@ Correctness is a must. The other goals are strong defaults and win in this order
 - **Performance**: recording, setup matching and verification are hot paths with allocation-free fast paths (`FastMockInteractions`, the `Fast*Buffer` types). Measure hot-path changes with the benchmarks before and after.
 - **Public API**: every change to the public surface of `Mockolate` shows up in the API snapshots. Document new public members with XML comments. Mark breaking changes with `!` in the PR title (`feat!:`, `refactor!:`).
 - **Strong naming**: all assemblies are signed with `strongname.snk`; an `InternalsVisibleTo` needs `PublicKey="$(PublicKey)"`.
-- **Style**: follow `.editorconfig`: tabs, explicit types instead of `var`, `_camelCase` private fields, no `this.`, `System` usings first. Tests use xUnit with aweXpect (`await That(...)`).
+- **Style**: follow `.editorconfig`: tabs, explicit types instead of `var`, `_camelCase` private fields, no `this.`, `System` usings first. Tests use TUnit with aweXpect (`await That(...)`).
 
 ## Validation
 

Directory.Packages.props

@@ -28,12 +28,10 @@
 		<PackageVersion Include="Microsoft.SourceLink.GitHub" Version="10.0.401"/>
 	</ItemGroup>
 	<ItemGroup>
-		<PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.10.1"/>
 		<PackageVersion Include="BenchmarkDotNet" Version="0.15.8"/>
-		<PackageVersion Include="xunit" Version="2.9.3"/>
-		<PackageVersion Include="xunit.v3" Version="3.2.2"/>
-		<PackageVersion Include="xunit.runner.visualstudio" Version="3.1.5"/>
-		<PackageVersion Include="coverlet.collector" Version="10.1.0"/>
+		<PackageVersion Include="TUnit.Engine" Version="1.72.16"/>
+		<PackageVersion Include="Microsoft.Testing.Extensions.TrxReport" Version="2.5.1"/>
+		<PackageVersion Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.12.0"/>
 		<PackageVersion Include="aweXpect.Snapshots.PublicApi" Version="0.3.0"/>
 		<PackageVersion Include="aweXpect" Version="3.4.0"/>
 		<PackageVersion Include="aweXpect.Chronology" Version="1.1.0"/>

Docs/agents/workflows.md

@@ -12,15 +12,20 @@ The test projects reference the generator as an analyzer through a project refer
 
 ## Test
 
+The tests use TUnit on the Microsoft.Testing.Platform, which `global.json` selects as the runner of `dotnet test`. Each test project is an executable, so `dotnet run` works as well. The explicit tests (the snapshot acceptance tests) run only when the filter selects nothing but explicit tests.
+
 ```powershell
 # One project, all of its target frameworks
-dotnet test Tests/Mockolate.Tests
+dotnet test --project Tests/Mockolate.Tests
+
+# One framework and a tree node filter (/assembly/namespace/class/test, nested classes match with a wildcard)
+dotnet test --project Tests/Mockolate.Tests -f net10.0 --treenode-filter "/*/*/*IsTrueTests/*"
 
-# One framework and a name filter (VSTest filter syntax)
-dotnet test Tests/Mockolate.Tests -f net10.0 --filter "FullyQualifiedName~IsTrueTests"
+# The same without dotnet test
+dotnet run --project Tests/Mockolate.Tests -f net10.0 -- --treenode-filter "/*/*/*IsTrueTests/*"
 
 # Everything in the solution
-dotnet test Mockolate.slnx
+dotnet test --solution Mockolate.slnx
 ```
 
 Target frameworks per test project:
@@ -52,7 +57,7 @@ A newer language feature can compile for `net10.0` and fail for `net48`; build o
 After an intended change, overwrite the expected files with the explicit acceptance test and review the diff:
 
 ```powershell
-dotnet test Tests/Mockolate.SourceGenerators.Tests --filter "FullyQualifiedName~AcceptSnapshotChanges" -- xUnit.Explicit=only
+dotnet test --project Tests/Mockolate.SourceGenerators.Tests --treenode-filter "/*/*/*/AcceptSnapshotChanges"
 git diff -- Tests/Mockolate.SourceGenerators.Tests/Snapshot
 ```
 
@@ -67,7 +72,7 @@ To add a scenario, add an entry to `Scenarios` and run the acceptance test.
 - run the tests with `AWEXPECT_ACCEPT_SNAPSHOTS=all`.
 
 ```powershell
-dotnet test Tests/Mockolate.Api.Tests --filter "FullyQualifiedName~AcceptApiChanges" -- xUnit.Explicit=only
+dotnet test --project Tests/Mockolate.Api.Tests --treenode-filter "/*/*/*/AcceptApiChanges"
 ```
 
 Commit the updated snapshots with the change; never commit pending files.
@@ -96,13 +101,13 @@ CI runs one job per class: `CallbackBenchmarks`, `CompleteEventBenchmarks`, `Com
 
 ## Mutation Tests
 
-Stryker mutates `Source/Mockolate` against `Mockolate.Tests` and `Mockolate.Internal.Tests` on `net8.0` with mutation level `Advanced`. Outside `main` it only mutates code changed since `main`. A full run takes long; run it only when asked:
+Stryker mutates `Source/Mockolate` against `Mockolate.Tests` and `Mockolate.Internal.Tests` on `net8.0` with mutation level `Advanced`, through its runner for the Microsoft.Testing.Platform (`--test-runner mtp`). The version is the `dotnet-stryker` `PackageDownload` in `Pipeline/Build.csproj`. Outside `main` it only mutates code changed since `main`. A full run takes long; run it only when asked:
 
 ```powershell
-./build.ps1 MutationTestExecution
+./build.ps1 MutationTests
 ```
 
-Reports go to `Artifacts/Stryker`. The `MutationTests` target also prepares the PR comment and expects to run in GitHub Actions.
+Reports go to `Artifacts/Stryker`, together with the Markdown body of the PR comment. `MutationTestsComment` and `MutationTestsDashboard` post the comment and upload the report, and expect to run in GitHub Actions.
 
 ## Build Pipeline (Fallout)
 
@@ -111,14 +116,14 @@ Reports go to `Artifacts/Stryker`. The `MutationTests` target also prepares the
 | Target | Purpose |
 |---|---|
 | `Compile` | Restore and build the solution with the GitVersion-derived version |
-| `UnitTests` | Run `Build.Tests`, `Mockolate.Tests`, `Mockolate.Internal.Tests`, `Mockolate.Analyzers.Tests` and `Mockolate.SourceGenerators.Tests` for each framework (`net48` only on Windows) with coverage |
-| `CodeCoverage` | `UnitTests` plus a ReportGenerator OpenCover report in `TestResults/reports` |
+| `UnitTests` | Run `Build.Tests`, `Mockolate.Tests`, `Mockolate.Internal.Tests`, `Mockolate.Analyzers.Tests` and `Mockolate.SourceGenerators.Tests` for each framework (`net48` only on Windows), with a TRX and a Cobertura coverage file per project and framework in `TestResults` |
+| `CodeCoverage` | `UnitTests` plus a ReportGenerator SonarQube report in `TestResults/reports` |
 | `ApiChecks` | Run `Mockolate.Api.Tests` |
 | `CodeAnalysis` | SonarCloud analysis (needs `SonarToken`) |
 | `Pack` | Build the NuGet package into `Artifacts/Packages`, with a release-specific README |
 | `Benchmarks` | Run the benchmarks (`--benchmark-filter`, default `*`) and print the reports |
 | `BenchmarkComment`, `PublishBenchmarkReport` | CI only: PR comment and docs site data |
-| `MutationTests`, `MutationTestExecution`, `MutationTestComment`, `MutationTestDashboard` | Stryker run, PR comment and dashboard upload |
+| `MutationTests`, `MutationTestsComment`, `MutationTestsDashboard` | Stryker run, PR comment and dashboard upload |
 | `UpdateReadme` | Write the packaged README to `Artifacts/README.md` |
 
 ## CI Workflows

Pipeline/Build.ApiChecks.cs

@@ -21,8 +21,9 @@ partial class Build
 				.SetProcessEnvironmentVariable("DOTNET_CLI_UI_LANGUAGE", "en-US")
 				.EnableNoBuild()
 				.SetResultsDirectory(TestResultsDirectory)
-				.CombineWith(cc => cc
-					.SetProjectFile(project)
-					.AddLoggers($"trx;LogFileName={project.Name}.trx")), completeOnFailure: true);
+				.AddProcessAdditionalArguments(
+					$"--project \"{project.Path}\"",
+					"--report-trx",
+					$"--report-trx-filename {project.Name}.trx"));
 		});
 }

Pipeline/Build.CodeCoverage.cs

@@ -17,7 +17,7 @@ partial class Build
 				.SetProcessToolPath(NuGetToolPathResolver.GetPackageExecutable("ReportGenerator", "ReportGenerator.dll",
 					framework: "net10.0"))
 				.SetTargetDirectory(TestResultsDirectory / "reports")
-				.AddReports(TestResultsDirectory / "**/coverage.cobertura.xml")
+				.AddReports(TestResultsDirectory / "**/*.cobertura.xml")
 				// The generic format of Sonar lists the lines per file. A format that lists them per method leaves out the
 				// lines of a lambda in a generic class, because ReportGenerator keeps them in a class without methods.
 				.AddReportTypes(ReportTypes.SonarQube)

Pipeline/Build.MutationTests.cs

@@ -92,8 +92,9 @@ partial class Build
 				File.WriteAllText(configFile, configText);
 				Log.Debug($"Created '{configFile}':{Environment.NewLine}{configText}");
 
+				// The unit tests are executables of the Microsoft.Testing.Platform, which the default runner (VSTest) cannot run.
 				string arguments =
-					$"-f \"{configFile}\" -O \"{strykerOutputDirectory}\" -r \"Markdown\" -r \"cleartext\" -r \"json\"";
+					$"-f \"{configFile}\" -O \"{strykerOutputDirectory}\" -r \"Markdown\" -r \"cleartext\" -r \"json\" --test-runner mtp";
 
 				string executable = EnvironmentInfo.IsWin ? "dotnet-stryker.exe" : "dotnet-stryker";
 				IProcess process = ProcessTasks.StartProcess(

Pipeline/Build.UnitTest.cs

@@ -36,17 +36,21 @@ partial class Build
 					.SetConfiguration(Configuration)
 					.SetProcessEnvironmentVariable("DOTNET_CLI_UI_LANGUAGE", "en-US")
 					.EnableNoBuild()
-					.SetDataCollector("XPlat Code Coverage")
 					.SetResultsDirectory(TestResultsDirectory)
 					.CombineWith(
 						UnitTestProjects,
 						(settings, project) => settings
-							.SetProjectFile(project)
 							.CombineWith(
 								project.GetTargetFrameworks()?.Except(excludedFrameworks),
 								(frameworkSettings, framework) => frameworkSettings
 									.SetFramework(framework)
-									.AddLoggers($"trx;LogFileName={project.Name}_{framework}.trx")
+									.AddProcessAdditionalArguments(
+										$"--project \"{project.Path}\"",
+										"--report-trx",
+										$"--report-trx-filename {project.Name}_{framework}.trx",
+										"--coverage",
+										"--coverage-output-format cobertura",
+										$"--coverage-output {project.Name}_{framework}.cobertura.xml")
 							)
 					), completeOnFailure: true
 			);

Pipeline/Build.csproj

@@ -27,12 +27,10 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<PackageDownload Include="coverlet.console" Version="[3.1.2]"/>
 		<PackageDownload Include="dotnet-sonarscanner" Version="[9.0.2]"/>
 		<PackageDownload Include="dotnet-stryker" Version="[5.0.0]"/>
 		<PackageDownload Include="GitVersion.Tool" Version="[6.0.5]"/>
 		<PackageDownload Include="ReportGenerator" Version="[5.4.1]"/>
-		<PackageDownload Include="xunit.runner.console" Version="[2.9.2]"/>
 	</ItemGroup>
 
 </Project>