assertEquals("EXAMPLE.COM", auth.getUserDomain());
        }

        @Test
        @DisplayName("getUserDomain: explicit realm overrides")
        void getUserDomain_fromExplicitRealm() {
            Kerb5Authenticator auth = new Kerb5Authenticator(new Subject());
            auth.setRealm("REALM.TEST");
            assertEquals("REALM.TEST", auth.getUserDomain());
        }