Document how to test that you're instrumenting traces correctly

[cartermp]

Something I've seen come up a few times is: "How do I unit test that I'm adding the right attributes to a span?"

You can't test this with the tracing API because it doesn't give you access to this data. But you can depend on the "SDK trace API" in a language to get access to a read/write span.

This should probably be documented with an example in all the languages with stable tracing:

• JS
• Java
• Go
• .NET
• Python
• Elixir
• Ruby
• C++

[cartermp]

Some specific things that would be covered:

• How to establish a test harness with an in-memory exporter
• Which packages to pull in to do this testing
• Example of a simple bit of code that does a thing with otel tracing
• Example of a test that tests that function that does the tracing

[wildefires]

@cartermp and I have been discussing this on the pollinators slack - I'm happy to write up some docs for Go if someone would be kind enough to point me to where they should live :)

[svrnm]

Put it in a subpage of https://opentelemetry.io/docs/instrumentation/go/, we can then still decide to move it somewhere else.

[akasprzok]

I wrote a rough draft of I think what this issue is asking for in https://temporaryhack.com/blog/opentelemetry-testing, for elixir.

Happy to take some feedback on it, polish it, and submit it -- if it's what y'all are looking for.

[svrnm]

I wrote a rough draft of I think what this issue is asking for in https://temporaryhack.com/blog/opentelemetry-testing, for elixir.

Happy to take some feedback on it, polish it, and submit it -- if it's what y'all are looking for.

Can you put it as a (draft) PR here? makes the review easier for us.

[akasprzok]

I wrote a rough draft of I think what this issue is asking for in https://temporaryhack.com/blog/opentelemetry-testing, for elixir.
Happy to take some feedback on it, polish it, and submit it -- if it's what y'all are looking for.

Can you put it as a (draft) PR here? makes the review easier for us.

Done, submitted rough draft here

[cartermp]

Thanks @akasprzok - your doc is live!

[svrnm]

@cartermp: can we copy some of the content from elixir/erlang over to the other languages or is it too specific?

[cartermp]

The content can probably be copied over easily and tweaked as needed, but the code samples will be different since setting up a test harness can vary so wildly from language to language.

[akasprzok]

Thank you all for making my first contribution such a fantastic experience!