Undefined method 'instantiate_observers' error after restarting spork server

Question

I was running tests using spork with no problem, however, occasionally I have to restart the spork server to get it to recognize newly added routes. On this occasion, I restarted the spork server, and I am now getting the following error message whenever I run any tests:

Exception encountered: #<NoMethodError: undefined method `instantiate_observers' for ActiveRecord::Base:Class>
backtrace:
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/activerecord-4.0.0/lib/active_record/dynamic_matchers.rb:22:in `method_missing'
/Users/mydocs/Documents/rails_projects/sample_app_rails_4/spec/spec_helper.rb:56:in `block in <top (required)>'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork.rb:69:in `call'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork.rb:69:in `block in exec_each_run'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork.rb:69:in `each'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork.rb:69:in `exec_each_run'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/run_strategy/forking.rb:12:in `block in run'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/forker.rb:21:in `block in initialize'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/forker.rb:18:in `fork'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/forker.rb:18:in `initialize'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/run_strategy/forking.rb:9:in `new'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/run_strategy/forking.rb:9:in `run'
/Users/mydocs/.rvm/gems/ruby-2.0.0-p247@railstutorial_rails_4_0/gems/spork-1.0.0rc3/lib/spork/server.rb:48:in `run'
/Users/mydocs/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/drb/drb.rb:1588:in `perform_without_block'
/Users/mydocs/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/drb/drb.rb:1548:in `perform'
/Users/mydocs/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/drb/drb.rb:1626:in `block (2 levels) in main_loop'
/Users/mydocs/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/drb/drb.rb:1622:in `loop'
/Users/mydocs/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/drb/drb.rb:1622:in `block in main_loop'

Additional restarts of the spork server have not changed anything. Any thoughts on what may be causing this/how to fix it? Thanks

EDIT: Added code from spec_helper.rb

Spork.each_run do
  ActiveSupport::Dependencies.clear
  ActiveRecord::Base.instantiate_observers  <--- This is line 56

  load "#{Rails.root}/config/routes.rb"
  Dir["#{Rails.root}/app/**/*.rb"].each { |f| load f }  
end if Spork.using_spork?

This block was added so that I would no longer need to reset the spork server to get it to recognize changes to routes, however, I made this change earlier today and have successfully run many tests since then.

Answer 1

Observers were removed from Rails 4. Attempting to instantiate them will just not work. The code example you have is probably from Rails 3.

Remove that line. Nothing bad will happen.