Url generation issue

action_controller_master.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

require 'rails'
require 'action_controller/railtie'

class TestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: 'cookie_store_key'
  config.secret_token    = 'secret_token'
  config.secret_key_base = 'secret_key_base'

  config.logger = Logger.new($stdout)
  Rails.logger  = config.logger

  routes.draw do
    resources :parents do
      resources :children
    end

    resources :others
  end
end

class ChildrenController < ActionController::Base
  include Rails.application.routes.url_helpers

  def index
    render text: parent_children_path
  rescue ActionController::UrlGenerationError
    render text: 'OK'
  end
end

class OthersController < ActionController::Base
  include Rails.application.routes.url_helpers

  def index
    render text: parent_children_path
  rescue ActionController::UrlGenerationError
    render text: 'OK'
  end
end

require 'minitest/autorun'
require 'rack/test'

class BugTest < Minitest::Test
  include Rack::Test::Methods

  def test_raises_without_parent_id
    get '/others'
    assert_equal 'OK', last_response.body
  end

  def test_raises_with_parent_id
    get '/parents/foo/children'
    assert_equal 'OK', last_response.body
  end

  private
    def app
      Rails.application
    end
end

test output

Failure:
BugTest#test_raises_with_parent_id [action_controller_master.rb:67]:
Expected: "OK"
  Actual: "/parents/foo/children"