Audience { static Audience empty() { return new Audience(Collections.emptyList()); } private  Audience(final List<String> principles); Optional<String> getSinglePrinciple(); List<String> getPrinciples(); @Override boolean equals(@Nullable final Object o); @Override int hashCode(); @Override String toString();  }
@Test public void empty() { final Audience emptyAudience = Audience.empty(); assertThat(emptyAudience.getPrinciples()).isEmpty(); }