This is an example how to test the telemetry data using MockServer.

The example contains a simple SpringBoot application that exposes an API available at GET http://localhost:8080/ping

When the API is called, auto instrumentation from the OpenTelemetry Java Agent records traces and metrics.

The method doWork() in Controller class is annotated with the @WithSpan annotation which automatically generates the trace when the method is called. Counter meter apiCounter increments the metric on each API call.

• Java 1.8 or higher

Go to test folder and execute the test from ApplicationTest class.

ApplicationTest contains 1 test testTelemetry() which verifies that:

• the traces Controller.doWork and Controller.ping were sent to the collector
• metric apiCounter was sent to the collector

when the API was called.

Gradle build script contains a task to download the OpenTelemetry Java Agent jar, which is added to the jvm arguments in the test task.

Additionally, the OpenTelemetry is configured with properties:

• otel.exporter.otlp.protocol=http/protobuf - set up the telemetry protocol, default is grpc
• otel.metric.export.interval=5000 - set up the interval, between the start of two export attempts, default is 60s More information about the configuration can be found in this OpenTelemetry doc.

The MockServer library is used to mock the collector web server. It's configured with port 4318, because for http/protobuf protocol, the otel exporter endpoint is by default set to http://localhost:4318.

The collector mock server is configured with expectation to reply with http code 200 on every request.

To verify that the telemetry was sent to the collector we retrieve the requests from the mock server and assert the traces and metrics names.