ActionCable testing with Capybara

Gemfile

# 3.7.0 has some issues with `port` option
gem 'puma', '>= 3.7.1'

group :test do
  # starting from 2.7.0 Capybara allows to specify the named server to use
  gem 'capybara', '>= 2.7.0'

  # just for reference
  gem 'selenium-webdriver'
end

action_cable_feature_spec.rb

# spec/features/action_cable_feature_spec.rb

require 'capybara_helper'

RSpec.feature 'Action cable integration spec', type: :feature do
  it 'changed value appears without page refreshing', js: true do
    value = 'New Value'
    
    visit root_path
    expect(page).not_to have_content(value) # sanity check
    
    # submit form in new window
    new_window = window_opened_by { click_link 'Page with form' }
    within_window new_window do
      fill_in 'Value', with: value
      click_on 'Save'
    end
    
    # check for new value in previous window without page refreshing
    switch_to_window(windows.first)
    expect(page).to have_text(value)
  end
end

cable.yml

# config/cable.yml

# You might also need your ActionCable features to work in rails console:
#
# >> ActionCable.server.broadcast 'example_channel', message: '<p>Test</p>'
# [ActionCable] Broadcasting to example_channel: {:message=>"<p>Test</p>"}
# => []
#
# The default behavior for ActionCable in development mode is to use the async adapter,
# which operates within the same process only. For inter-process broadcasting, you will need to switch to the redis adapter.

redis: &default
  adapter: redis
  url: redis://localhost:6379/1

production: *default
development: *default
test: *default

capybara_helper.rb

# spec/capybara_helper.rb

require 'rails_helper'
require 'capybara/rspec'

# specify js driver
Capybara.javascript_driver = :selenium

# for testing ActionCable with Capybara we need a multithreaded webserver
Capybara.server = :puma