only extend main object for top level dsl

lib/sinatra/main.rb

@@ -25,4 +25,6 @@ module Sinatra
   at_exit { Application.run! if $!.nil? && Application.run? }
 end
 
-include Sinatra::Delegator
+# include would include the module in Object
+# extend only extends the `main` object
+extend Sinatra::Delegator

test/integration/app.rb

@@ -1,6 +1,20 @@
 require 'sinatra'
 
+configure do
+  set :foo, :bar
+end
+
 get '/app_file' do
   content_type :txt
   settings.app_file
-end
+end
+
+get '/mainonly' do
+  object = Object.new
+  begin
+    object.send(:get, '/foo') { }
+    'false'
+  rescue NameError
+    'true'
+  end
+end

test/integration_test.rb

@@ -44,9 +44,13 @@ class IntegrationTest < Test::Unit::TestCase
     Process.kill("TERM", pipe.pid) if pipe
   end
 
-  it 'starts a top level application' do
+  def assert_content(url, content)
     with_server do
-      assert_equal open("http://127.0.0.1:#{port}/app_file").read, app_file
+      response = open("http://127.0.0.1:#{port}#{url}")
+      assert_equal response.read, content
     end
   end
+
+  it('sets the app_file') { assert_content "/app_file", app_file }
+  it('only extends main') { assert_content "/mainonly", "true"   }
 end