class Rack::Test::Session

def restore_state

exiting the block.
cookie jar to the state they were prior to block execution upon
Yield to the block, and restore the last request, last response, and 
def restore_state
  request = @last_request
  response = @last_response
  cookie_jar = @cookie_jar.dup
  after_request = @after_request.dup
  begin
    yield
  ensure
    @last_request = request
    @last_response = response
    @cookie_jar = cookie_jar
    @after_request = after_request
  end
end