autocompletion.rb

# spec/support/autocompletion.rb
module Autocompletion
  def select_autocompletion(value, from:, with:, multiple: false)
    input_field = find_field(from)
    input_value = multiple ? "#{input_field.value}#{with}" : with
    
    # fill_in input[:id], with: input_value
    # input_field.trigger(:keydown)
    
    page.execute_script "$('##{input_field[:id]}').val('#{input_value}').trigger('keydown')"
    find('.ui-menu-item', text: value).trigger(:click)
  end
end

awesome_feature_spec.rb

# spec/features/awesome_feature_spec.rb

feature 'an awesome feature' do
  scenario 'an awesome scenario with auto-complete-iness', :js do
    # setup
    # ...
    select_autocompletion 'Autocompletion', from: 'Field label', with: 'auto'
    # ...
    # verify and teardown
  end
end

rails_helper.rb

# spec/rails_helper.rb

# Make sure autocompletion.rb is loaded (you may already have something like this)
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }

RSpec.configure do |config|
  # ...
  config.include Autocompletion, type: :feature
end