### Question:
MillenniumDomainPrincipal implements Principal, Serializable { public String getDomainName() { return domainName; } MillenniumDomainPrincipal(final String username, final String domainName); String getDomainName(); @Override String getName(); String getUsername();  }### Answer:
@Test public void testGetDomainName() { assertThat(principal.getDomainName()).isEqualTo(domainName); }