env.rb

Capybara.register_driver :poltergeist_inspector do |app|
  Capybara::Poltergeist::Driver.new(app, :inspector => true)
end

Before('@javascript', '@inspector') do
  Capybara.javascript_driver = :poltergeist_inspector
end

output.txt

  @javascript @inspector
  Scenario: Previewing a new template        # features/accounts/templates.feature:23
    Given I am a new, authenticated operator # features/step_definitions/login_steps.rb:53
    And I am on the plan page                # features/step_definitions/navigation_steps.rb:1
:poltergeist_inspector
    When I preview a new template            # features/step_definitions/template_steps.rb:38
      To use the remote debugging, you have to launch the driver with `:inspector => true` configuration option (Capybara::Poltergeist::Error)
      ./features/step_definitions/template_steps.rb:41:in `/^I preview a new template$/'
      features/accounts/templates.feature:26:in `When I preview a new template'
    Then I should see the new template PDF   # features/step_definitions/template_steps.rb:92

Failing Scenarios:
cucumber features/accounts/templates.feature:23 # Scenario: Previewing a new template

some_steps.rb

When(/^I preview a new template$/) do
  click_on 'add-template'
  p Capybara.javascript_driver
  page.driver.debug
  # (...)
end

the_feature.feature

  @javascript @inspector
  Scenario: Previewing a new template
    Given I am a new, authenticated operator
    And I am on the plan page
    When I preview a new template
    Then I should see the new template PDF