Test with tracing

[Darksonn]

We currently don't run any tests with tracing enabled.

[hawkw]

I'm assuming the goal here is just to ensure that the tests pass with the "tracing" feature flag enabled, rather than to actually collect tracing output from these tests? If we wanted to collect output for debugging the tests, we would also need to add a tracing-subscriber dev-dependency and set up a subscriber in the tests to collect the emitted traces.

This looks good, though, if the goal is just to ensure the feature doesn't break stuff!

[Darksonn]

I just wanted the tests to run. For example, there's a test that the header is not too large which we didn't run at all with the extra tracing id.

[carllerche]

Very good, thanks