MSTest 4.5 and Microsoft.Testing.Platform 2.5 Enable UI Testing for UWP and WinUI 3 Apps

Enhanced UI Testing Capabilities

MSTest 4.5 and Microsoft.Testing.Platform (MTP) 2.5 now provide a UI-thread testing pattern for Universal Windows Platform (UWP) and WinUI 3 applications. This allows test setup, asynchronous test code, and cleanup to execute with direct access to the UI thread, which is necessary for reliable UI testing.

The supported application models include classic and modern UWP, as well as packaged or unpackaged WinUI 3 apps, and WinUI hosts utilizing AppContainer.

Simplified Test Execution

MSTest.Sdk automatically determines the appropriate launch path for each app model. It directly starts unpackaged applications and uses Microsoft.Testing.Extensions.PackagedApp to register and activate packaged apps via their Application User Model ID (AUMID). For AppContainer hosts, it also grants necessary access to the controller and report pipes.

Instead of the initial test tool, MSTest.Sdk launches a full-trust sidecar controller. This controller manages test arguments, cancellation requests, reports, retries, and the final exit code, then initiates the app hosting the tests. This approach bypasses the use of Microsoft.NET.Test.Sdk, vstest.console, UwpTestHostRuntimeProvider, or Visual Studio deployment runtime.

Configuration and Considerations

To enable packaged activation for unsigned build outputs, Developer Mode or a similar sideloading policy is required. AppContainer tests should be run non-elevated, and the policy on the Continuous Integration (CI) agent must be confirmed.

For WinUI applications, starting unpackaged is recommended unless specific behaviors like package identity, packaged activation contracts, or an exact match with installed app behavior are under test. UWP applications are inherently packaged and sandboxed.

Adopting the New Framework

Developers can select MSTest.Sdk and MTP for UWP and WinUI 3 apps by configuring global.json at the solution or repository root. This involves pinning MSTest.Sdk 4.5 and selecting Microsoft.Testing.Platform for the native .NET 10 dotnet test experience. Without this configuration, .NET 10 defaults to VSTest.