withWorker() lacks testing

[OlliV]

There is no test coverage at all because it's a bit challenging thing to test. It's currently not possible to even start it in jest because the trampoline code cannot be loaded.

[Kikobeats]

do you think could be worth it to delegate worker threads implementation details to piscina?

e.g., https://github.com/piscinajs/fastify-piscina/blob/current/plugin.js#L7

[Kikobeats]

I think this example is pretty accurate:
https://github.com/piscinajs/piscina/tree/current/examples/server