signed_cookies.rb

# 
# An improvement on http://stackoverflow.com/a/9094206/284612
#
# Place this file in spec/support/signed_cookies.rb
#
module SignedCookies
  def signed_cookie(name, opts={})
    verifier = ActiveSupport::MessageVerifier.new(request.env["action_dispatch.secret_token".freeze])
    if opts[:value]
      @request.cookies[name] = verifier.generate(opts[:value])
    else
      verifier.verify(cookies[name])
    end
  end
end

spec_helper.rb

# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}

RSpec.configure do |config|
  # omitted...

  # Include our #signed_cookie helper method in our controller specs
  config.include SignedCookies, :type => :controller
end