Testing for a thumbnail in a view

image.feature

Then I should see the thumbnail "ponies.png"

image_steps.rb

Then /^I should see the thumbnail "([^\"]*)"$/ do |filename|
  thumbnail = ::News::Thumbnail.find_by_filename!(filename)
  response.should have_tag("img[src=?][class=thumbnail]", %r{#{thumbnail.public_filename + '?.*'}})
end