docker-compose.yml

version: "3.6"

services:
  app:
    build: ..
    depends_on:
      - selenium
    environment:
      SELENIUM_HOST: selenium

  selenium:
    image: selenium/standalone-chrome
    shm_size: 2g

spec-support-capybara.rb

Capybara.configure do |config|
  config.default_driver = :selenium

  # We use remote in docker compose to drive headless chrome in another container
  selenium_host = ENV.fetch("SELENIUM_HOST", "127.0.0.1")
  selenium_port = ENV.fetch("SELENIUM_PORT", "4444")

  # Selenium container needs to talk back to us, but docker-compose run
  # doesn't use a stable hostname, so listen on all addresses and ask for the
  # current hostname and tell selenium to connect back on that. Also add the
  # ephemeral port to all `visit` urls, etc.
  config.server = :puma
  config.server_host = "0.0.0.0"
  config.app_host = "http://#{Socket.gethostname}"
  config.always_include_port = true

  Capybara.register_driver :selenium do |app|
    Capybara::Selenium::Driver.new app,
      browser: :remote,
      url: "http://#{selenium_host}:#{selenium_port}/wd/hub",
      desired_capabilities: Selenium::WebDriver::Remote::Capabilities.chrome
  end
end