OpenTelemetry

This feature requires the Microsoft.Testing.Extensions.OpenTelemetry NuGet package.

This extension integrates OpenTelemetry with Microsoft.Testing.Platform (MTP), allowing test runs to emit traces and metrics through the standard OpenTelemetry SDK.

Note

This extension is available in MTP starting with version 2.1.0.

Important

Starting with MTP 2.4.0, the OpenTelemetry extension follows the MTP release version and its public entry points are no longer experimental.

Choose provider ownership

Choose whether MTP or your application owns the OpenTelemetry providers.

Use MTP-owned providers

Disable the auto-generated entry point (<GenerateTestingPlatformEntryPoint>false</GenerateTestingPlatformEntryPoint>) and call AddOpenTelemetryProvider in your Main method:

var builder = await TestApplication.CreateBuilderAsync(args);

builder.AddOpenTelemetryProvider(
    withTracing: tracing => tracing
        .AddTestingPlatformInstrumentation()
        .AddConsoleExporter(),
    withMetrics: metrics => metrics
        .AddTestingPlatformInstrumentation()
        .AddConsoleExporter()
);

using var app = await builder.BuildAsync();
return await app.RunAsync();

To configure instrumentation, resource attributes, and an OTLP exporter from standard OTEL_* environment variables, call:

builder.AddOpenTelemetryProviderFromEnvironment();

The method adds instrumentation only when you configure an exporter or pass a configuration callback, so you can leave the registration in the application when some environments don't export telemetry.

Use application-owned providers

Starting with MTP 2.5 preview, call AddTestingPlatformDiagnostics when your application already configures OpenTelemetry through Aspire ServiceDefaults, Microsoft.Extensions.Hosting, or another composition root. This method activates the Microsoft.Testing.Platform activity source and meter without creating, flushing, or disposing a TracerProvider or MeterProvider.

Subscribe the application-owned provider with AddTestingPlatformInstrumentation on its tracing and metrics builders. The application retains ownership of its providers, exporters, resource identity, and disposal.

For an MSBuild-generated hosted entry point, reference Microsoft.Testing.Extensions.Hosting, set TestingPlatformHostFactory to the host factory method, and set:

<TestingPlatformOpenTelemetryMode>HostOwned</TestingPlatformOpenTelemetryMode>

HostOwned calls only AddTestingPlatformDiagnostics; it doesn't create providers or replace the host's resource identity. For host lifecycle and factory requirements, see Host integration.

API

AddTestingPlatformDiagnostics

Activates MTP's activity source and meter for application-owned listeners or OpenTelemetry providers without transferring provider ownership to MTP.

AddOpenTelemetryProvider

Registers the OpenTelemetry provider on ITestApplicationBuilder. Accepts two optional callbacks:

• withTracing: configures the TracerProviderBuilder for distributed tracing.
• withMetrics: configures the MeterProviderBuilder for metrics collection.

AddTestingPlatformInstrumentation

Call on TracerProviderBuilder or MeterProviderBuilder to subscribe to the built-in Microsoft.Testing.Platform activity source and meter.

AddTestingPlatformResource

Call on ResourceBuilder to add test assembly, host, operating system, and runtime attributes. The detector also identifies CI provider, pipeline, branch, and commit information for GitHub Actions, Azure Pipelines, GitLab CI, and Jenkins.

Focused resource helpers

For an application-owned provider, call AddTestingPlatformTestResource to add test-specific identity and AddTestingPlatformCIResource to add CI and source-control provenance. These focused helpers don't replace application-owned service.*, host.*, os.*, or process.* attributes.

AddOpenTelemetryProviderFromEnvironment

Registers tracing, metrics, resource detection, and an OTLP exporter from standard OpenTelemetry environment variables. OTEL_SDK_DISABLED=true disables the integration. Configure OTEL_TRACES_EXPORTER, OTEL_METRICS_EXPORTER, or OTEL_EXPORTER_OTLP_ENDPOINT to activate export.

Activity source and meter

The extension emits telemetry under:

• Activity source: Microsoft.Testing.Platform
• Meter: Microsoft.Testing.Platform

Semantic conventions

MTP emits standard OpenTelemetry testing and code attributes where a convention exists, including test.case.name, test.case.result.status, test.suite.name, code.function.name, code.file.path, code.line.number, code.stacktrace, and error.type. Failed tests set the span status to Error and add an exception event.

MTP extends the conventions with additional result states (skipped, error, timeout, cancelled, and unknown) and test attributes for concepts that OpenTelemetry doesn't define. To preserve existing dashboards, legacy attribute and instrument names remain enabled by default.

When the launching process supplies TRACEPARENT and TRACESTATE, MTP places the test run under that trace instead of starting an unrelated root trace.

MSTest execution spans

Starting with MSTest 4.5 and MTP 2.5 preview, native MSTest runs use one canonical MTP-owned activity for each test execution. MSTest makes the activity current while it runs the test constructor, initialization, test method, cleanup, and custom TestMethodAttribute code. Automatically instrumented HttpClient, SQL, Entity Framework, WCF, and custom activities therefore become children of the test activity.

MTP adds the final result, timing, output, and artifacts to the same activity and stops it at the execution end time recorded by MSTest. This behavior avoids duplicate framework and result spans and prevents asynchronous result processing from inflating the test duration.

Test frameworks that don't use the canonical execution API retain the compatibility topology: the framework execution activity and MTP result activity remain siblings, and the result activity links to the activity that was current when the framework published the in-progress update.

Emitted metrics

Instrument	Type	Unit	Description
test.case.duration	Histogram	s	Test duration, grouped by result status and suite.
test.case.result.count	Counter	{test}	Completed tests, grouped by result status and suite.
test.case.active	UpDownCounter	{test}	Tests that are currently running.
test.run.duration	Histogram	s	Run duration, grouped by result status and exit code.
test.case.retry.count	Counter	{test}	Tests scheduled for another attempt by the retry extension.

Environment configuration

Environment variable	Default	Description
TRACEPARENT, TRACESTATE	Unset	W3C trace context for the parent run.
TESTINGPLATFORM_OTEL_CAPTURE_TEST_OUTPUT	1	Attaches captured standard output and error to test spans. Set to 0 when output might contain secrets.
TESTINGPLATFORM_OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT	8192	Sets the maximum characters retained for a string attribute.
TESTINGPLATFORM_OTEL_EMIT_LEGACY_ATTRIBUTES	1	Emits legacy attribute and instrument names alongside semantic-convention names.
OTEL_SDK_DISABLED	Unset	Set to true to disable the OpenTelemetry SDK.
OTEL_SERVICE_NAME	Unset	Overrides the service name.
OTEL_EXPORTER_OTLP_ENDPOINT	Unset	Sets the OTLP endpoint.
OTEL_TRACES_EXPORTER, OTEL_METRICS_EXPORTER	Unset	Selects trace and metric exporters.