ScalaTest OpenTelemetry Reporter

ScalaTest extension that instruments your tests with OpenTelemetry.

Getting Started

This example demonstrates how to send trace data to Jaeger in localhost.

Before you start, you need to run Jaeger in a Docker container.

services:
  jeager:
    image: jaegertracing/all-in-one:latest
    ports:
      - "4317:4317"
      - "16686:16686"

docker compose up -d

Add the following configuration to your build.sbt.

lazy val `my-project` = (project in file("my-project"))
  .settings(
    // Add dependencies
    libraryDependencies ++= Seq(
      "org.scalatest"           %% "scalatest"                   % "3.2.18"       % Test,
      "io.opentelemetry"         % "opentelemetry-sdk"           % "1.38.0"       % Test,
      "io.opentelemetry"         % "opentelemetry-exporter-otlp" % "1.38.0"       % Test,
      "io.opentelemetry.semconv" % "opentelemetry-semconv"       % "1.21.0-alpha" % Test,
      "dev.nomadblacky"         %% "scalatest-otel-reporter"     % "<version>"    % Test,
    ),
    // Add the reporter class
    Test / testOptions += Tests.Argument(
      TestFrameworks.ScalaTest,
      "-C",
      "example.JaegerTestReporter",
    ),
  )

Create a reporter class that extends OpenTelemetryTestReporter and implements the otel method.
Below is an example of sending trace data to Jaeger in localhost.

package example

import dev.nomadblacky.scalatest_otel_reporter.OpenTelemetrySdkTestReporter
import io.opentelemetry.api.OpenTelemetry
import io.opentelemetry.api.common.Attributes
import io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter
import io.opentelemetry.sdk.OpenTelemetrySdk
import io.opentelemetry.sdk.resources.Resource
import io.opentelemetry.sdk.trace.SdkTracerProvider
import io.opentelemetry.sdk.trace.`export`.BatchSpanProcessor
import io.opentelemetry.semconv.ResourceAttributes

import java.util.concurrent.TimeUnit

// Mix-In OpenTelemetryTestReporter
class JaegerTestReporter extends OpenTelemetrySdkTestReporter {
  def initOpenTelemetry: OpenTelemetrySdk = {
    // Direct trace data to Jaeger on localhost
    val jaegerOtlpExporter =
      OtlpGrpcSpanExporter.builder.setEndpoint("http://localhost:4317").setTimeout(30, TimeUnit.SECONDS).build

    // Configure the service name (recommended)
    val serviceNameResource =
      Resource.create(Attributes.of(ResourceAttributes.SERVICE_NAME, "scalatest-otel-demo-manual"))

    // Configure the SpanProcessor
    val tracerProvider = SdkTracerProvider.builder
      .addSpanProcessor(BatchSpanProcessor.builder(jaegerOtlpExporter).build)
      .setResource(Resource.getDefault.merge(serviceNameResource))
      .build

    // Return OpenTelemetry instance
    OpenTelemetrySdk.builder.setTracerProvider(tracerProvider).build
  }
}

Implement the test as usual.

package example

import org.scalatest.funsuite.AnyFunSuiteLike

class SimpleTests extends AnyFunSuiteLike {
  test("sum") {
    assert(1 + 1 == 2)
  }
  test("sub") {
    assert(1 - 1 == 0)
  }
}

class FailedTests extends AnyFunSuiteLike {
  test("failed assertion") {
    assert(1 + 1 == 3)
  }
  test("throw an exception") {
    throw new RuntimeException("An exception occurred")
  }
}
// ...

Execute the test in the sbt shell.

sbt
> my-project/test

Open the Jaeger UI in your browser (http://localhost:16686/) and you will see the trace data.

Configuration

You can configure the behavior of the reporter by ScalaTest's config map.

Test / testOptions += Tests.Argument(
  TestFrameworks.ScalaTest,
  "-C",
  "example.JaegerTestReporter",
  "-Dscalatest-otel-reporter.root-span-name=my-awesome-tests",
)

Key	Description	Default
scalatest-otel-reporter.root-span-name	The name of the root span.	scalatest

Posts

• テストでも Observability したいっ！ ScalaTest を OpenTelemetry で計装してみた (ScalaMatsuri 2024 Unconference)