Running headless ChromeForTesting for your Cuke/Capybara tests

env.rb

# This setup in features/support/env.rb works both locally in and CI for me.  

# IN your Gemfile's `test` environment, add 
#   gem 'simplecov-json', require: false
# and run `bundle install` to get it.

# these steps must be at very top of features/support/env.rb *and* spec/rails_helper.rb:
require 'simplecov'  
SimpleCov.start 'rails'
if ENV['CCTR']   # are we running in CI or locally? (see gist [https://gist.github.com/armandofox/6273653fa68744d720842e6a6e5be04f] )
  require "simplecov_json_formatter"
  SimpleCov.formatter = SimpleCov::Formatter::JSONFormatter
else
  # running locally; make nice HTML output to browse coverage interactively
  SimpleCov.formatter = SimpleCov::Formatter::HTMLFormatter
end


# In CI, I set the envariables CHROMEDRIVER_PATH and CHROME_FOR_TESTING_PATH based on using
#  an existing Github Action that installs those binaries.
# When running locally, these variables are NOT set, but I have both ChromeForTesting and Chromedriver 
#  (matching versions) installed in the tmp/ directory in the root of the app.
# Note carefully where `path_to_chromedriver` and `path_to_chrome_for_testing` are
#  subsequently used in lines 15 and later.

path_to_chromedriver =       ENV['CHROMEDRIVER_PATH'] ||
                             `find ~+/tmp -type f -name 'chromedriver'`.chomp

path_to_chrome_for_testing = ENV['CHROME_FOR_TESTING_PATH'] ||
                             `find ~+/tmp -type f -name 'Google Chrome for Testing'`.chomp

if (path_to_chromedriver.blank? || path_to_chrome_for_testing.blank?)
  abort "Cannot find Chromedriver and/or ChromeForTesting binaries. Check wiki for instructions."
end

Capybara.register_driver :selenium_chrome_headless do |app|
  options = Selenium::WebDriver::Chrome::Options.new.tap do |opts|
    opts.add_argument '--headless'
    opts.add_argument '--no-sandbox'
    opts.add_argument '--disable-gpu'
    opts.add_argument '--window-size=1024,1024'
    # When an "unexpected" alert/confirm is displayed, accept it (ie user clicks OK).
    # Expected ones can be handled with accept_alert do...end or accept_confirm do...end
    opts.unhandled_prompt_behavior = :accept
    opts.binary = path_to_chrome_for_testing
  end

  # expects headless Chrome-for-testing and its driver to be in $RAILS_ROOT/tmp somewhere,
  # but puppeteer installs them in arch-specific subdirs :-(
  Capybara::Selenium::Driver.new(
    app,
    browser: :chrome,
    service: Selenium::WebDriver::Service.chrome(path: path_to_chromedriver),
    options: options,
    clear_session_storage: true,
    clear_local_storage: true)
end
# note that I use headless *only* for scenarios marked @javascript.  Otherwise it uses the much faster Rack::Test.
# To accomplish that, set `Capybara.javascript_driver` rather than just `Capybara.driver`.
Capybara.javascript_driver = :selenium_chrome_headless