categories_controller.rb

  def index
    @category = Category.find(:all)
    @cat = Category.new
    respond_to do |format|
      format.html
      format.xml  { render :xml  => @category } 
      format.json { render :json => @category }
    end  
  end

  def create
    @category = Category.new(params[:category])
      if @category.save(params)
        flash[:notice] = 'Category successfully added !'
        redirect_to '/categories'
      else
        flash[:notice] = 'There was an error processing your request'
        render :action => "index"
      end
  end

categories_controller_test.rb

  context "on POST to :create " do
    setup { post :create, :category => { :name  => 'Flowers', :description => 'I Like flowers' } }
    
    should_assign_to :category
    should_set_the_flash_to "Category successfully added !"
  end
  
  context "on POST to :create without values" do
    setup { post :create,
                 :category => { :name  => nil, :description => nil } }
    
    should_assign_to :category
    should_set_the_flash_to "There was an error processing your request"
    should_render_template :index
  end