How to test the instrumentation in an application using Golang test?

[ethernoy]

Given that we have a application that has three functions A, B and C, where A always calls B, B always calls C and C calls nothing else. In each of the function, a span is created using opentelemetry-go instrumentation.

How can we correctly use go test to test that in one call of A, all three spans are created correctly? I noticed that we may use a otlp-collector to serve as a span collector, but I believe this is quite an overkill.

[dmathieu]

You can use the provider oteltest package, which includes an InMemory Span Exporter.
Configure your tracer provider with that exporter, run your code. And all spans will be available with the GetSpans method.

[ethernoy]

Thank you so much. One thing to notice though: better use WithSyncer instead of WithBatcher when setting the exporter in TracerProvider, otherwise the GetSpan call may have inconsistent response.

[dmathieu]

Obviously, yes.

[sdavispluto]

Why was oteltest removed? The deprecation message says to use tracetest, but that module doesn't include metrics. Is there another way to test metrics, now that oteltest is removed?

[dmathieu]

There is metricdatatest, which allows comparison of collected metrics: https://pkg.go.dev/go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest