start {
                succeeds("a")
                instant.aDone
                succeeds("b")
            }
            request1.waitUntilBlocked()
            instant.aBlocked
            request1.release()
            request2.waitUntilBlocked()
            request2.release()
        }
        server.stop()

        then:
        instant.aDone > instant.aBlocked
    }

     */
    public interface BlockingRequest extends ExpectedRequest {
        /**
         * Waits for the request to be received and blocked.
         */
        void waitUntilBlocked();

        /**
         * Unblock the request.
         */
        void release();
    }

    /**
     * Allows the test to synchronise with and unblock requests.
     */