@Test
void sortedByKey() {

    final Comparator<Map.Entry<String, Integer>> comparator = Map.Entry.comparingByKey(); // Java's type inference can be improved...
    final List<Map.Entry<String, Integer>> expected = refStream().sorted(comparator.reversed()).collect(Collectors.toList());
    final List<Map.Entry<String, Integer>> actual = instance.sortedByKey(Comparator.reverseOrder()).toList();
    assertEquals(expected, actual);
}