MSTest.Extensions.Hosting

MSTest.Extensions.Hosting

MSTest.Extensions.Hosting lets an application-owned Microsoft.Extensions.Hosting container create MSTest test classes.

This package remains prerelease, including in MSTest RTM builds, while its Microsoft.Testing.Extensions.Hosting dependency is alpha.

Register the integration while building the same host that runs Microsoft Testing Platform:

HostApplicationBuilder builder = Host.CreateApplicationBuilder();
builder.Services.AddSingleton<MyApplicationService>();
builder.Services.AddMSTestTestClassInjection();

Test classes can then request registered services in a public constructor:

[TestClass]
public sealed class MyTests(MyApplicationService service, TestContext testContext)
{
    [TestMethod]
    public void UsesApplicationService()
        => Assert.IsNotNull(service);
}

The integration is explicit and affects only MSTest test-class construction. It creates one IServiceScope for every test invocation, including each data row and retry attempt. TestInitialize, the test method, and TestCleanup share the same test-class instance and scope. Static ClassInitialize and ClassCleanup run outside invocation scopes.

The application host remains caller-owned. MSTest never disposes the host or its root service provider. After TestCleanup, the integration disposes the test-class instance and then its invocation scope.

NativeAOT, browser WebAssembly, AOT compilation, and MSTest source generation are not supported by this first reflection-based integration. Calling AddMSTestTestClassInjection in one of those modes produces a deterministic build error, including when host registration is compiled into a referenced project.