# Terminal
gem install rails -v '4.2.10'
gem install rails -v '5.0.0'
rails _4.2.10_ new rails4210
rails _5.0.0_ new rails500
git diff rails4210 rails500 > rails_4.2.10-rails_5.0.0.diff
rake test
rake stats
bundle update rails
rails test
rake rails:update # older way
rails app:update # same thing, but newer way

# Gemfile
gem 'rails', '~>5.0.0'

group :test do 
  gem 'simplecov', require: false
  gem 'rails-controller-testing'
end

# tests/test_helper.rb
ENV['RAILS_ENV'] ||= 'test'

require 'simplecov'
SimpleCov.start

require File.expand_path('../../config/environment', __FILE__)
require 'rails/test_help'

class ActiveSupport::TestCase
  # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
  fixtures :all

  # Add more helper methods to be used by all tests here...
end