Using RSPEC and Paperclip together to create a photo

Hey,

I have paperclip working well and users can upload a photo and a description (this is not treebook).

the app works greeat but im trying to get a test to pass (using SPEC).

before I write some validations im creating a design and defining the design attributes (like description and photo) but I don't know how to mark the correct photo extension or string. For description i just can set it equal to a string like "Lorem ipsum", but i dont know what to do for an image

here is my design_spec

describe Design do

let(:user) { FactoryGirl.create(:user) }
before { @design = user.designs.build(description: "Lorem ipsum", photo:(this is where i need help) ) }

subject { @design }

it { should respond_to(:description) }
it { should respond_to(:user_id) }
it { should have_attached_file(:photo) }
  it { should validate_attachment_presence(:photo) }
  it { should respond_to(:user) }
  its(:user) { should eq user }

    it { should be_valid }

describe "when user_id is not present" do
    before { @design.user_id = nil }
    it { should_not be_valid }
end

end

You can see where I need help in the code with the THIS IS WHERE I NEED HELP text.

Thank you in advance for the help Cheers, justin