<p><%= link_to "Delete my account", registration_path(resource_name), :data => { :confirm => "Are you sure?" }, :method => :delete %></p>

scenario 'user deletes account' do
   make_user_and_login
   click_link('Account Settings')
   page.should have_selector('title', :text => 'Account Settings')
   click_link('Delete my account')
   # Are You Sure?
   # click OK in confirm box
   # page.should etc.....
end

page.driver.browser.switch_to.alert.accept

page.driver.browser.switch_to.alert.dismiss

page.evaluate_script('window.confirm = function() { return true; }')

page.should have_content "Account deleted"