It works for me,
first i removed the comment for config.frameworks -= [ :active_record ] in 'config/environment.rb'
then i added comments inside the file 'config/initializers/new_rails_defaults.rb.'

Now it works for me.

But i cannot understand what to do in test/test_helper.rb.

my test_helper.rb is like this

ENV["RAILS_ENV"] = "test"
require File.expand_path(File.dirname(__FILE__) + "/../config/environment")
require 'test_help'
class ActiveSupport::TestCase
self.use_transactional_fixtures = true
self.use_instantiated_fixtures = false
fixtures :all
end

Please tell me the purpose of the test_helper.rb file and what to do now