caboose

I've been playing with rspec on a project and I gotta say, I'm in love. I'm working up to a full-blown article, but if you haven't checked it out, please do. Rspec really helps you see ruby as a message-based language. You're just passing messages around. So it's easy to set up an expectation, "this object should receive this message", and then fake out a response in order to test the logic in our application. For those of you who've been meaning to get around to it, here's the executive summary. (Go read the docs, they really are excellent) h2. behaviour-based Your specs set up expectations, like

   User.should_receive(:count) 

but can also return a value

   User.should_receive(:count).and_return(0)

This helps you test your logic, since you can determine any return value you like. In case you haven't got it, that's the same as doing

  User.stub!(:count).and_return(0)

except using should_receive is like an assertion, where it'll raise if the User class never receives that message. This means stub! is well suited to setup blocks. The counter-intuitive thing for you test::unit types is that you set up the expectations before calling the method.

context "The cart controller"
  setup do
    @user = mock("user")
    @carts = mock("carts")
    @cart = mock("cart")
  end

  specify "should render checkout with cart specified correctly" do
    @user.should_receive(:carts).and_return(@carts)
    @carts.should_receive(:find).with('1').and_return(@cart)
    @cart.should_receive(:waiting_for_address_info?).and_return(true)
    
    get :checkout, :id => 1
    response.should_be_success
  end
end

Nowhere here are we hitting the model, since that's been well tested earlier. We just ensure that the model and the association gets the correct messages, and that the logic in the controller is solid. The controller code looks something like

  def checkout
    @cart = params[:id] ? @person.carts.find(params[:id]) : @person.find_unfinished_cart  
    @cart.shipping_address ||= Address.new
    @cart.begin_checkout!
    redirect_to :action => 'address', :id => @cart unless (@cart.active? or @cart.waiting_for_address_info?)
  end

Oh, and one more tip. If you're doing something like

  redirect_to :id => @cart

You'll want to stub @cart.to_param to an ID.

  @cart = mock("cart")
  @cart.stub!(:to_param).and_return('1')