Imported from josejaviercanon/RulesEngineEditor_BE (RulesEngineEditor.Server/.opencode/skills/dotnet-test/skills/migrate-vstest-to-mtp/SKILL.md). Install upstream with npx skills add josejaviercanon/RulesEngineEditor_BE --skill migrate-vstest-to-mtp. Copyright stays with the author (MIT).

VSTest -> Microsoft.Testing.Platform Migration

Migrate a .NET test solution from VSTest to Microsoft.Testing.Platform (MTP). The outcome is a solution where all test projects run on MTP, dotnet test works correctly, and CI/CD pipelines are updated.

Important: Do not mix VSTest-based and MTP-based .NET test projects in the same solution or run configuration -- this is an unsupported scenario.

When to Use

• Switching from VSTest to Microsoft.Testing.Platform for any supported test framework
• Enabling dotnet run / dotnet watch / direct executable execution for test projects
• Enabling Native AOT or trimmed test execution
• Replacing vstest.console.exe with dotnet test on MTP
• Updating CI/CD pipelines from the VSTest task to the .NET Core CLI task
• Updating dotnet test arguments from VSTest syntax to MTP syntax

When Not to Use

• The project already runs on Microsoft.Testing.Platform and there is no remaining MTP behavioral difference to resolve (e.g., exit code 8 for zero tests discovered)
• Migrating between test frameworks (e.g., MSTest to xUnit.net) -- different effort entirely
• The project builds UWP or packaged WinUI test projects -- MTP does not support these yet
• The solution mixes .NET and non-.NET test adapters (e.g., JavaScript or C++ adapters) -- VSTest is required
• Upgrading MSTest versions -- use migrate-mstest-v1v2-to-v3 or migrate-mstest-v3-to-v4

Inputs

Workflow

Step 1: Assess the solution

1. Identify the test framework for each test project -- see the platform-detection skill for the package-to-framework mapping. Key indicators:
   • MSTest: References MSTest or MSTest.TestAdapter, or uses MSTest.Sdk (with <IsTestApplication> not set to false). Note: MSTest.TestFramework alone is a library dependency, not a test project.
   • NUnit: References NUnit3TestAdapter
   • xUnit.net: References xunit and xunit.runner.visualstudio
2. Check the .NET SDK version (dotnet --version) -- this determines how dotnet test integrates with MTP
3. Check whether a Directory.Build.props file exists at the solution or repo root -- all MTP properties should go there for consistency
4. Check for vstest.console.exe usage in CI scripts or pipeline definitions
5. Check for VSTest-specific dotnet test arguments in CI scripts: --filter, --logger, --collect, --settings, --blame*
6. Run dotnet test to establish a baseline of test pass/fail counts

Step 2: Set up Directory.Build.props

Critical: Set MTP runner properties in Directory.Build.props at the solution or repo root whenever possible, rather than per-project. This prevents inconsistent configuration where some projects use VSTest and others use MTP (an unsupported scenario). Note: MTP also requires test projects to have <OutputType>Exe</OutputType>. Only MSTest.Sdk sets this automatically. For all other setups (MSTest NuGet packages with EnableMSTestRunner, NUnit with EnableNUnitRunner, xUnit.net with YTest.MTP.XUnit2), prefer setting <OutputType>Exe</OutputType> centrally in Directory.Build.props with a condition that targets only test projects. If you cannot reliably target only test projects from Directory.Build.props, setting <OutputType>Exe</OutputType> per-project is an acceptable exception.

Conditioning in Directory.Build.props: Do NOT use Condition="'$(IsTestProject)' == 'true'" -- IsTestProject is set by the test SDK targets later in evaluation and is not available when Directory.Build.props is imported. Use a property that is available early, such as MSBuildProjectName, to target test projects by naming convention. For example, if all test projects end in .Tests:

<PropertyGroup Condition="$(MSBuildProjectName.EndsWith('.Tests'))">
  <OutputType>Exe</OutputType>
</PropertyGroup>

Adjust the condition (e.g., .EndsWith('Tests'), .Contains('.Test')) to match the test project naming convention used in the repository.

Step 3: Enable the framework-specific MTP runner

Each framework has its own opt-in property. Add these in Directory.Build.props for consistency.

MSTest

Option A -- MSTest NuGet packages (3.2.0+):

<PropertyGroup>
  <EnableMSTestRunner>true</EnableMSTestRunner>
  <OutputType>Exe</OutputType>
</PropertyGroup>

Ensure the project references MSTest 3.2.0 or later. If the version is already 3.2.0+, no MSTest version upgrade is needed for MTP migration.

Option B -- MSTest.Sdk:

When using MSTest.Sdk, MTP is enabled by default -- no EnableMSTestRunner or OutputType Exe property is needed (the SDK sets both automatically). The only action is: if the project has <UseVSTest>true</UseVSTest>, remove it. That property forces the project to use VSTest instead of MTP.

NUnit

Requires NUnit3TestAdapter 5.0.0 or later.

1. Update NUnit3TestAdapter to 5.0.0+:

<PackageReference Include="NUnit3TestAdapter" Version="5.0.0" />

1. Enable the NUnit runner:

<PropertyGroup>
  <EnableNUnitRunner>true</EnableNUnitRunner>
  <OutputType>Exe</OutputType>
</PropertyGroup>

xUnit.net

Add a reference to YTest.MTP.XUnit2 -- this package provides MTP support for xUnit.net v2 projects without requiring an upgrade to xunit.v3. You must also set OutputType to Exe:

<PackageReference Include="YTest.MTP.XUnit2" Version="0.4.0" />

<PropertyGroup>
  <OutputType>Exe</OutputType>
</PropertyGroup>

Note: YTest.MTP.XUnit2 preserves the VSTest --filter syntax, so no filter migration is needed for xUnit.net v2. It also supports --settings for runsettings (xunit-specific configurations only), xunit.runner.json, TRX reporting via --report-trx, and --treenode-filter.

xUnit.net v3

xUnit.net v3 (xunit.v3 package) has built-in MTP support. Enable it with:

<PropertyGroup>
  <UseMicrosoftTestingPlatformRunner>true</UseMicrosoftTestingPlatformRunner>
</PropertyGroup>

Important: xUnit.net v3 on MTP does NOT support the VSTest --filter syntax. You must translate filters to xUnit.net v3's native filter options (see Step 5).

Step 4: Configure dotnet test integration

The dotnet test integration depends on the .NET SDK version.

.NET 10 SDK and later (recommended)

Use the native MTP mode by adding a test section to global.json:

{
  "sdk": {
    "version": "10.0.100"
  },
  "test": {
    "runner": "Microsoft.Testing.Platform"
  }
}

In this mode, dotnet test arguments are passed directly -- for example, dotnet test --report-trx.

Important: global.json does not support trailing commas. Ensure the JSON is strictly valid.

.NET 9 SDK and earlier

Use the VSTest mode of dotnet test command to run MTP test projects by adding this property in Directory.Build.props:

<PropertyGroup>
  <TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
</PropertyGroup>

Important: In this mode, you must use -- to separate dotnet test build arguments from MTP arguments. For example: dotnet test --no-build -- --list-tests.

Step 5: Update dotnet test command-line arguments

VSTest-specific arguments must be translated to MTP equivalents. Build-related arguments (-c, -f, --no-build, --nologo, -v, etc.) are unchanged.

Filter migration

MSTest, NUnit, and xUnit.net v2 (with YTest.MTP.XUnit2): The VSTest --filter syntax is identical on both VSTest and MTP. No changes needed.

xUnit.net v3 (native MTP): xUnit.net v3 does NOT support the VSTest --filter syntax on MTP. You must translate filters to xUnit.net v3's native filter options.

xUnit.net v3 filter flags

Multiple values can be specified with a single flag: --filter-class Foo Bar.

VSTest → xUnit.net v3 filter translation table

xUnit.net v3 query filter language

For complex expressions, use --filter-query with a path-segment syntax:

/<assemblyFilter>/<namespaceFilter>/<classFilter>/<methodFilter>[traitName=traitValue]

Each segment matches against: assembly name, namespace, class name, method name. Use * for "match all" in any segment. Documentation: https://xunit.net/docs/query-filter-language

Translation example

# VSTest
dotnet test --filter "FullyQualifiedName~IntegrationTests&Category=Smoke"

# xUnit.net v3 MTP -- using individual filters (AND behavior)
dotnet test -- --filter-class *IntegrationTests* --filter-trait "Category=Smoke"

# xUnit.net v3 MTP -- using query language (assembly/namespace/class/method[trait])
dotnet test -- --filter-query "/*/*/*IntegrationTests*/*[Category=Smoke]"

Note: When combining --filter-class and --filter-trait, both conditions must match (AND behavior). For complex expressions, use --filter-query with the path-segment syntax. See the xUnit.net query filter language docs for full reference.

Step 6: Install MTP extension packages (if needed)

If CI scripts use TRX reporting, crash dumps, or hang dumps, add the corresponding NuGet packages:

<!-- TRX report generation (replaces --logger trx) -->
<PackageReference Include="Microsoft.Testing.Extensions.TrxReport" Version="1.6.2" />

<!-- Crash dump collection (replaces --blame-crash) -->
<PackageReference Include="Microsoft.Testing.Extensions.CrashDump" Version="1.6.2" />

<!-- Hang dump collection (replaces --blame-hang) -->
<PackageReference Include="Microsoft.Testing.Extensions.HangDump" Version="1.6.2" />

<!-- Code coverage (replaces --collect "Code Coverage") -->
<PackageReference Include="Microsoft.Testing.Extensions.CodeCoverage" Version="17.13.0" />

Step 7: Update CI/CD pipelines

Azure DevOps

If using the VSTest task (VSTest@3): Replace with the .NET Core CLI task (DotNetCoreCLI@2):

# Before (VSTest task)
- task: VSTest@3
  inputs:
    testAssemblyVer2: '**/*Tests.dll'
    runSettingsFile: 'test.runsettings'

# After (.NET Core CLI task)
- task: DotNetCoreCLI@2
  displayName: Run tests
  inputs:
    command: 'test'
    arguments: '--no-build --configuration Release'

If already using DotNetCoreCLI@2: Update arguments per Step 5 translations. Remember the -- separator on .NET 9 and earlier:

- task: DotNetCoreCLI@2
  displayName: Run tests
  inputs:
    command: 'test'
    arguments: '--no-build -- --report-trx --results-directory $(Agent.TempDirectory)'

GitHub Actions

Update dotnet test invocations in workflow files with the same argument translations from Step 5.

Replace vstest.console.exe

If any script invokes vstest.console.exe directly, replace it with dotnet test. The test projects are now executables and can also be run directly.

Step 8: Handle behavioral differences

Zero tests exit code

VSTest silently succeeds when zero tests are discovered. MTP fails with exit code 8. Options:

• Pass --ignore-exit-code 8 when running tests
• Add to Directory.Build.props:

<PropertyGroup>
  <TestingPlatformCommandLineArguments>$(TestingPlatformCommandLineArguments) --ignore-exit-code 8</TestingPlatformCommandLineArguments>
</PropertyGroup>

• Use environment variable: TESTINGPLATFORM_EXITCODE_IGNORE=8

Step 9: Remove VSTest-only packages (optional)

Once migration is complete and verified, remove packages that are only needed for VSTest:

• Microsoft.NET.Test.Sdk -- not needed for MTP (MSTest.Sdk v4 already omits it by default)
• xunit.runner.visualstudio -- only needed for VSTest discovery of xUnit.net (not needed when using YTest.MTP.XUnit2)
• NUnit3TestAdapter VSTest-only features -- the adapter is still needed but only for the MTP runner

Note: If you need to maintain VSTest compatibility during a transition period, keep these packages.

Step 10: Verify

1. Run dotnet build -- confirm zero errors
2. Run dotnet test -- confirm all tests pass
3. Compare test pass/fail counts to the pre-migration baseline
4. Run the test executable directly (e.g., ./bin/Debug/net8.0/MyTests.exe) -- confirm it works
5. Verify CI pipeline produces the expected test result artifacts (TRX files, code coverage, crash dumps)
6. Test that Test Explorer in Visual Studio (17.14+) or VS Code discovers and runs tests

Validation

• All test projects use MTP runner (no VSTest-only configuration remains)
• dotnet build completes with zero errors
• dotnet test passes all tests and test counts match pre-migration baseline
• Test executable runs directly (e.g., ./bin/Debug/net8.0/MyTests.exe)
• CI pipeline produces expected test result artifacts (TRX files, code coverage, crash dumps)
• Test Explorer in Visual Studio or VS Code discovers and runs tests
• No vstest.console.exe invocations remain in CI scripts
• <OutputType>Exe</OutputType> is set for all non-MSTest.Sdk test projects

Common Pitfalls

Next Steps

• Use run-tests for running tests on the new MTP platform
• Use mtp-hot-reload for iterative test fixing with hot reload on MTP

More Info

• Test platforms overview
• Migrate from VSTest to Microsoft.Testing.Platform
• Microsoft.Testing.Platform overview
• Testing with dotnet test
• Microsoft.Testing.Platform CLI options
• Microsoft.Testing.Platform extensions