ruby-on-rails - xpath can't find anything in rspec test

Question

UPDATE 2 - adding before(:each) block

before(:each) do
    ...
    post_via_redirect(
        sub_domain(
            path: login_view_path(
                @p
            ), 
            subdomain: @account.subdomain
        ),
        first_name: "Capybara",
        last_name: "RSpec"
    )

    expect(response).to render_template(:show)
end

---

UPDATE

response.body has the data I'm looking for
but page.html only has a doctype.

---

ORIGINAL

I'm trying to do some integration testing. I have this:

require "spec_helper"

feature "Tracking without Javascript" do
    ...
    scenario "when navigating to a content" do
        ...
        # this passes so I know there is a body
        expect(response.body).to include(c.name)

        find(:xpath, "/html") # see if xpath works...
    end
end

and I get the error:

 Failure/Error: find(:xpath, "/html")
 Capybara::ElementNotFound:
   Unable to find xpath "/html"

any ideas?