gistfile1.rb

  def test_should_rollback_any_changes_if_an_exception_occurred_while_saving
    before = [@pirate.catchphrase, @pirate.ship.name]

    @pirate.catchphrase = 'Arr'
    @pirate.ship.name = 'The Vile Insanity'

    # Stub the save method of the @pirate.ship instance to raise an exception
    class << @pirate.ship
      def save(*args)
        super
        raise 'Oh noes!'
      end
    end

    assert_raise(RuntimeError) { assert !@pirate.save }
    assert_equal before, [@pirate.reload.catchphrase, @pirate.ship.name]
  end