How to mount any Rack based application into Rack::App

app.rb

require 'rack/app'
require './rack_based_application.rb'

class App < Rack::App
  
  mount_rack_based_application RackBasedApplication

  namespace :mount do
    mount_rack_based_application RackBasedApplication, :to => '/point'
  end
  
end

app_spec.rb

require 'spec_helper'
describe  do
  
  include Rack::App::Test 
  rack_app App
  
  it { expect(get('/').body).to eq 'endpoints have bigger priority than mounted applications' }
  
  it { expect(get('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(post('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(put('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(delete('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(patch('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(head('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  it { expect(options('/hello/world/test/endpoint').body).to eq 'Hello, World!' }
  
  it 'should mount to the correct namespace and mount point' do
    expect(get('/mount/point/hello/world/test/endpoint').body).to eq 'Hello, World!'
  end
  
  it { expect(get('/hello/world/to_you').body).to eq 'partially matching endpoint' }

end

config.ru

require './app'
run App

rack_based_application.rb

class RackBasedApplication

  def self.call(env)
    new.call(env)
  end

  def call(env)

    request_path = env[::Rack::PATH_INFO]

    if request_path == '/'
      ['200', {'Content-Type' => 'text/html'}, ['static endpoint']]

    elsif request_path =~ /^\/users\/.*/
      ['200', {'Content-Type' => 'text/html'}, ['dynamic endpoint']]

    elsif request_path == '/hello/world/test/endpoint'
      ['200', {'Content-Type' => 'text/html'}, ['Hello, World!']]

    else
      ['404', {}, ['404 Not Found!']]

    end

  end

end

spec_helper.rb

require 'rack/app/test'
require_relative '../app'