User defined finders for Capybara

finders.rb

Capybara.add_selector(:link) do
  xpath {|rel| ".//a[contains(@rel, '#{rel}')]"}
end

some_html_file.html

<a href="javascript:void(0);" rel="toggle-chart">Toggle chart</a>

some_step_file.rb

When /^I toggle the charts$/ do
  page.find(:link, "toggle-chart").click
end

@shinzui offered up via Twitter the "contains" option from XPath. Using that method allows you to have multiple values set in the "rel" attribute (e.g. rel="foo bar baz"). You can then do find(:link, "foo") and not have to match all the values in the "rel" attribute. You can find other XPath functions here: http://www.w3.org/TR/xpath/#corelib

Another note: If you are up to date on Capybara, you can use css matchers instead and avoid all this mess.