stop_stream_from causes undefined method 'pubsub'

[ghost]

What Ruby, Rails and RSpec versions are you using?

Ruby version: 2.7.2
Rails version: 6.1.3.1
RSpec version: 3.10

Observed behaviour

Full write-up in Rails repo under issue rails/rails#41077

[pirj]

Have you had a chance to investigate the root cause, @jasonatball ?
A pull request is welcome.

[ghost]

Reproduceable on rails 6.1.3.1. Reproduction steps:

Install rails, rails new blog. Update Gemfile to add rspec-rails to test group:

group :test do
  gem 'rspec-rails', "~> 4.0.0"

Install rspec: rails generate rspec:install

Add following method to app/channels/application_cable/channel.rb:

module ApplicationCable
  class Channel < ActionCable::Channel::Base
    def subscribed
      stream_from uuid
      stop_stream_from uuid # This causes the error
    end
  end
end

Create following spec/channels/channel_spec.rb

require "rails_helper"
RSpec.describe ApplicationCable::Channel, :type => :channel do
  it "subscribes" do
    stub_connection uuid: '12345'
    subscribe()
  end
end

Run spec: rspec spec\channels\channel_spec.rb

Observe error:

Failures:

  1) ApplicationCable::Channel subscribes
     Failure/Error: stop_stream_from uuid

     NoMethodError:
       undefined method `pubsub' for #<ActionCable::Channel::ConnectionStub:0x000000000bd0d8a0>
     # ./app/channels/application_cable/channel.rb:5:in `subscribed'
     # ./spec/channels/channel_spec.rb:6:in `block (2 levels) in <top (required)>'

Finished in 0.04651 seconds (files took 10.52 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/channels/channel_spec.rb:4 # ApplicationCable::Channel subscribes

Fix issue by adding code to channel_spec.rb:

module ActionCable
  module Channel
    class ConnectionStub
      def pubsub
        ActionCable.server.pubsub
      end
    end
  end
end

[ghost]

Not sure if always defering to ActionCable.server.pubsub via ConnectionStub pubsub is the correct solution but this worked for me.