int idx = bld.add(pref);
assertThat(idx, equalTo(0));
assertThat(bld.size(), equalTo(1));
PackedPreferenceData data = bld.build();
assertThat(data.size(), equalTo(1));
IndexedPreference p2 = data.preference(0);
assertThat(p2, equalTo(pref));
assertThat(p2.getIndex(), equalTo(0));
assertThat(p2.getUserIndex(), equalTo(0));
assertThat(p2.getItemIndex(), equalTo(0));
}