Add a way to actually test the action cable connection (with dummy app?)

[NullVoxPopuli]

Not sure how best to do this, or how far along action cable testing has come since this project was started, but there needs to be a way to actually test the communication with an action cable server. I think this might involve the use of a dummy app in the test folder, but am unsure if there is an elegant way to isolate action cable configurations between tests.

See the coverage report for things need testing.
This should be the last thing to get this project to 100% test coverage.

[Undo1]

Hasn't come very far, from what I've seen: rails/rails#23211