Write a test case require 'rack/client_spec' class LobsterSpec < Rack::ClientSpec::TestCase # <-- test case def test_flip # <-- test method get '/' do |req, res| # <-- expect request assert { res.status == 200 } end get '/?flip=left' do |req, res| # <-- expect request assert { req['HTTP_REFERER'] == 'http://localhost:9292/' } end end end