Run all rails tests in isolation

rails_tests_in_isolation.rb

require 'benchmark'
require 'socket'

ENV["RAILS_ENV"] = "test"

# Add test folder to load path
$: << './test'

puts Benchmark.measure{ 
  # Assuming test_helper requires config/environment
  require './test/test_helper'

}

Dir["#{Rails.root}/test/**/*_test.rb"].each do |file|
  # Check AR connection. For some reason it disconnects after running tests
  ActiveRecord::Base.verify_active_connections!
  pid = fork do
    require file
  end
  Process.wait(pid)
end