Rails: Playing with the DOM using Cucumber and Webrat

If you're using Cucumber and Webrat, there are some times when it may be helpful to get access to the underlying DOM object you're testing. It's easy to test that a tag has a specific attribute:
response.should have_selector("img.photo", :src => photo_path(@photo))
However, it's a lot harder if you want to get access to the img tag, get its src attribute, and test something about that src attribute without hard coding the exact value:
within("img.photo") do |img|
# Using ".dom" is the key.
url = img.dom["src"]
# Now, do more tests against the URL itself.