Stop disabling sessions in test environement

Manually `disable :sessions` if you want to manually pass in
the `rack.session` env key in your tests.

lib/sinatra/base.rb

@@ -916,7 +916,7 @@ module Sinatra
       # an instance of the class new was called on.
       def new(*args, &bk)
         builder = Rack::Builder.new
-        builder.use Rack::Session::Cookie if sessions? && !test?
+        builder.use Rack::Session::Cookie if sessions?
         builder.use Rack::CommonLogger    if logging?
         builder.use Rack::MethodOverride  if methodoverride?
         builder.use ShowExceptions        if show_exceptions?

test/helpers_test.rb

@@ -188,15 +188,22 @@ class HelpersTest < Test::Unit::TestCase
 
     it 'creates a new session when none provided' do
       mock_app {
+        enable :sessions
+
         get '/' do
           assert session.empty?
           session[:foo] = 'bar'
-          'Hi'
+          redirect '/hi'
+        end
+
+        get '/hi' do
+          "hi #{session[:foo]}"
         end
       }
 
       get '/'
-      assert_equal 'Hi', body
+      follow_redirect!
+      assert_equal 'hi bar', body
     end
   end