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