RSpec:Controllers:can the 'have_tag' be used in Controller testing?

Other sources indicate that one should be getting back html content in the response.body attribute:
- Action Pack 0.7.5: On rails from request to response

* Easy testing of both controller and template result through 
TestRequest/Response

     class LoginControllerTest < Test::Unit::TestCase
       def setup
         @request = ActionController::TestRequest.new
         @request.host = "http://somewhere"
       end

       def test_succesful_authentication
           @request.action = "authenticate"
           @request.request_parameters["user_name"] = "david"
           @request.request_parameters["password"]  = "secret"

           response = LoginController.process_test(@request)

           assert_equal(
             "http://somewhere/clients/", response.headers["location"])
           assert_equal Person.find(1), response.session["person"]
           assert(response.body.split("\n").include?(
             "<h1>You've been logged in!</h1>"))
       end
     end

   Learn more in link:classes/ActionController/TestRequest.html

It appears that this code snippet from a controller test (even though it's not RSpec) is able to get html from the response.body attribute.