spec_addon_helper.rb

def setup_env(env, environments)
  Rails.stub(:env).and_return(env)
  Rails.env.stub("#{env}?".to_sym).and_return(true)
  environments.map { |e| Rails.env.stub("#{e}?".to_sym).and_return(false) }
end

def stub_env(new_environment, environments = ["test", "development", "staging", "production"], &block)
  original_environment = Rails.env
  environments.delete(new_environment)

  setup_env(new_environment, environments)
  block.call
ensure
  environments.delete(original_environment)
  environments += [new_environment]

  setup_env(original_environment, environments)
end