Platform Detection

Test Platform and Framework Detection

Determine which test platform (VSTest or Microsoft.Testing.Platform) and which test framework (MSTest, xUnit, NUnit, TUnit) a project uses.

Response contract

When the requested output includes Platform:, report the platform that actually executes tests: VSTest or MTP. Do not put the dotnet test command mode on that line. If command mode matters, report it separately:

dotnet test mode: VSTest
Platform: MTP
Framework: MSTest

Thus an SDK 9 bridged project is Platform: MTP, even though its dotnet test mode is VSTest.

Detection files to always check (in order): global.json → .csproj → packages.config → Directory.Build.props → Directory.Packages.props

Detecting the project system

Classify the project before selecting a CLI:

• Root Sdk attribute or <Sdk> declaration: SDK-style.
• ToolsVersion, Microsoft.Common.props / Microsoft.CSharp.targets imports, explicit <Reference> and <Compile Include> items: classic non-SDK.
• packages.config: classic NuGet dependency management.

Classic projects can still use VSTest-compatible adapters, but dotnet test is not automatically a valid invocation. Preserve repository scripts/CI commands, commonly MSBuild followed by vstest.console.exe or MSTest.exe.

Detecting the test framework

Read the .csproj, adjacent packages.config, and Directory.Build.props / Directory.Packages.props and look for:

In classic projects, package IDs and versions may appear only in packages.config, while the project contains assembly <Reference> elements with HintPath values. Use both sources.

Detecting the test platform

Detect two separate axes:

1. dotnet test mode — VSTest mode or native MTP mode. This controls CLI syntax.
2. Executed test platform — VSTest or MTP. VSTest mode can bridge to and execute an MTP test application.

Run dotnet --version first because mode selection depends on the SDK.

Step 1: Detect dotnet test mode

• SDK 10+ with global.json "test": { "runner": "Microsoft.Testing.Platform" } → native MTP mode.
• SDK 10+ with runner VSTest or no test section → VSTest mode.
• SDK 8/9 → VSTest mode (the only dotnet test mode available).

Step 2: Detect the platform executed by that mode

When mode is native MTP, first verify that the project is an MTP application and has not explicitly opted into VSTest. A compatible project executes on MTP; a VSTest-only or opted-out project is a configuration conflict, not an MTP execution.

When mode is VSTest, first establish that an MTP runner is enabled (MSTest.Sdk, EnableMSTestRunner, EnableNUnitRunner with a compatible adapter, UseMicrosoftTestingPlatformRunner, or an MTP-only framework). Then check <TestingPlatformDotnetTestSupport> in the .csproj, Directory.Build.props, and Directory.Packages.props:

• MTP runner enabled and bridge true → the VSTest target redirects to InvokeTestingPlatform, so the executed platform is MTP. MTP arguments go after --.
• Runner or bridge absent → the bridge alone cannot create an MTP application; a dual-capable MSTest/NUnit project executes through VSTest by default.

Do not confuse the MSTest metapackage with the MSTest.Sdk project SDK. PackageReference Include="MSTest" plus EnableMSTestRunner=true enables the MSTest MTP runner, but it does not implicitly set TestingPlatformDotnetTestSupport. In VSTest command mode, execution remains on VSTest unless that bridge property evaluates to true.

MSTest.Sdk enables the MTP runner by default. Check its resolved version and evaluated properties for bridge behavior: versions such as 3.8 also set TestingPlatformDotnetTestSupport, while newer SDKs on .NET 10 may expect native MTP mode instead. <UseVSTest>true</UseVSTest> opts back into VSTest.

Critical: global.json decides command mode, not necessarily the executed platform. For example, SDK 10 with runner VSTest plus TestingPlatformDotnetTestSupport=true is VSTest mode executing MTP.

Microsoft.NET.Test.Sdk alone is not decisive; it can remain for compatibility in an MTP-enabled project. Key distinction: VSTest is the established platform that uses vstest.console under the hood. Microsoft.Testing.Platform (MTP) is the newer platform. In compatible SDK-style projects both can be invoked via dotnet test; classic projects may require their standalone runner.

Conflicting native-MTP and VSTest opt-out settings

If global.json selects native MTP command mode while a project explicitly opts out of MTP (for example, MSTest.Sdk with <UseVSTest>true</UseVSTest>), report the configuration conflict instead of pretending either platform can execute successfully. Recommend aligning the project and repository command mode; do not silently override either setting.

Conditional and per-target-framework properties

Evaluate runner and bridge properties for each target framework. If conditions produce different executed platforms, report each target explicitly (for example, net8.0: VSTest, net9.0: MTP) rather than collapsing the project to one global platform.