rails/actionpack/lib/action_controller/assertions/model_assertions.rb

require 'test/unit'
require 'test/unit/assertions'

module ActionController
  module Assertions
    module ModelAssertions
      # ensures that the passed record is valid by active record standards. returns the error messages if not
      def assert_valid(record)
        clean_backtrace do
          assert record.valid?, record.errors.full_messages.join("\n")
        end
      end
    end
  end
end