rspec

controller

  def new
  	slug = Slug.where(name: params[:slug_text]).first
    return redirect_to :root unless slug
    @place = slug.sluggable
    return redirect_to :root unless @place
  end

spec

describe ModerationController do
  describe "#new" do

    it "sends the query to the correct class" do
      place=stub(:place)
      Slug.should_receive(:where).with(name: "Paris").and_return(place)
      get :new, slug_text: "Paris"
    end

  end