@Test
public void setAllSetsAllSpecifiedFieldsWithoutDuplicates() {

    final Collection<JsonField> fieldsToBeSet = new ArrayList<>();
    Collections.addAll(fieldsToBeSet, eddard, cersei, robert, john, cersei, hodor, hodor);
    underTest.setAll(fieldsToBeSet);
    assertThat(underTest).containsExactly(eddard, cersei, robert, john, hodor);
}