works for me

require 'spec_helper'

# fake class
class ImageFake

end

describe "Image helper" do
  @sizes = [[300,400], [500,600], [700,800]]

  before :all do
    @image = ImageFake.new
  end

  @sizes.each do |width, height|
    context "desired image is #{width} x #{height}" do
      it "should produce an image of the correct size" do
        puts "#{width} x #{height}"
        puts "#{@image.class}"
      end
    end
  end
end