Interestingly, Rails doesn't see this in their test suite because they set this value during setup:

I’m going to add the API Server as an actor to my first test sequence to give some granularity as to what I’m actually testing.

For features like websocket interactions, a single full-stack smoke test is almost essential to confirm that things are going as planned, even if the individual parts of the interaction are also covered by unit tests.

How to test at the correct level?

As many things in life, deciding what to test at each level of testing is a trade-off:

Unit tests are usually cheap, and you should consider them like the basement of your house

A system test is often better than an integration test that is stubbing a lot of internals.

Only test the happy path, but make sure to add a test case for any regression that couldn’t have been caught at lower levels with better tests (for example, if a regression is found, regression tests should be added at the lowest level possible).

Black-box tests at the system level (aka end-to-end or QA tests)

Levels