@Test
public void message() throws Exception {

  Message message = messageFactory.messageBuilder()
      .body("Hi")
      .recipient("Bob")
      .subject("test");
  assertThat(message.sender, is("Alice"));
  assertThat(message.body, is("Hi"));
  assertThat(message.recipient, is("Bob"));
  assertThat(message.subject, is("test"));
  assertThat(messageUpdater(message).body("Goodbye").done().body,
      is("Goodbye"));
}