We have a distributed system and I am working on a ticket to add attributes to the Open Telemetry traces for NewRelic. In dotnet this is done by setting tags, like so:

Activity.Current.SetTag("bf.my_attribute", "myAttributeValue");

Because the messages are coming from MassTransit (MT), I created a custom Filter to add to the MT pipeline. So far so good. But given that this is part of a library and not the Service itself, I can only perform Unit tests, no integration ones.

My question is, how do I test it? The static Activity class is null in my tests. Any ideas?