How do I stub out the flickraw library in my app's unit tests?

Question

My Rails 2 app displays a slideshow of photos from Flickr via the flickraw library. My code works, but I'm stuck on how to properly write RSpec unit tests.

I have a Slide class that encapsulates everything that my app needs from flickraw. It acts somewhat like a model object but doesn't use ActiveRecord. It doesn't do much work; it delegates most of the heavy lifting to flickraw.

I haven't completed the tests because, as it is now, they require me to hard-code in some photo IDs from Flickr, and the tests would break if I rearranged my photoset or added new photos.

So my so-called unit tests are more like integration tests. I understand how to write a mock or stub using RSpec, but not sure how to do it to the flickraw library. How do I stub out flickraw and turn this into a unit test?

slide.rb:

require 'flickraw'
FlickRaw.api_key = "xxx"
FlickRaw.shared_secret = "yyy"
flickr.auth.checkToken :auth_token => "zzz"
PHOTOSET_ID = 123123123

class Slide
  attr_accessor :id, :previous_id, :next_id, :url_square, :url_thumbnail, :url_small, :url_medium500,
                :url_medium640, :url_large, :url_original

  def self.last
    photoset = flickr.photosets.getPhotos(:photoset_id => PHOTOSET_ID)
    Slide.new(photoset.photo.last.id)
  end

  def self.first
    photoset = flickr.photosets.getPhotos(:photoset_id => PHOTOSET_ID)
    Slide.new(photoset.photo.first.id)
  end

  def self.find(id)
    Slide.new(id)
  end

  def initialize(id)
    self.id = id
    photo = flickr.photos.getInfo(:photo_id => id)
    context = flickr.photosets.getContext(:photoset_id => PHOTOSET_ID, :photo_id => id)
    sizes = flickr.photos.getSizes(:photo_id => id)

    self.previous_id = (context.prevphoto.id == 0) ? nil : context.prevphoto.id
    self.next_id = (context.nextphoto.id == 0) ? nil : context.nextphoto.id

    sizes.each do |size|
      if size.label == "Square"
        self.url_square = size.source
      elsif size.label == "Thumbnail"
        self.url_thumbnail = size.source
      elsif size.label == "Small"
        self.url_small = size.source
      elsif size.label == "Medium"
        self.url_medium500 = size.source
      elsif size.label == "Medium 640"
        self.url_medium640 = size.source
      elsif size.label == "Large"
        self.url_large = size.source
      elsif size.label == "Original"
        self.url_original = size.source
      end
    end
  end
end

slide_spec.rb:

require 'spec_helper'

describe Slide do
  before(:each) do
    first_photo_id = "444555666"
    @slide = Slide.new(first_photo_id)
  end

  describe "urls" do
    it "should generate the thumbnail url" do
      @slide.url_thumbnail.should match(/_t.jpg$/)
    end

    it "should generate the small url" do
      @slide.url_small.should match(/_m.jpg$/)
    end

    it "should generate the medium500 url" do
      @slide.url_medium500.should match(/.jpg$/)
    end

    it "should generate the medium640 url" do
      @slide.url_medium640.should match(/_z.jpg$/)
    end

    it "should generate the large url" do
      @slide.url_large.should match(/_b.jpg$/)
    end

    it "should generate the original url" do
      @slide.url_original.should match(/_o.jpg$/)
    end
  end

  describe "finding" do
    it "should find the correct last photo" do
      # ???
    end

    it "should find the correct first photo" do
      # ???
    end
  end

  describe "context" do
    it "should return the correct previous photo" do
      # ???
    end

    it "should return the correct next photo" do
      # ???
    end
  end
end