new TestStringSortedSetGenerator() {
              @Override
              public SortedSet<String> create(String[] elements) {
                SortedSet<String> set = new TreeSet<>(arbitraryNullFriendlyComparator());
                Collections.addAll(set, elements);
                return set;
              }
            })
        .named("TreeSet, with comparator")
        .withFeatures(

            new TestStringSortedSetGenerator() {
              @Override
              public SortedSet<String> create(String[] elements) {
                SortedSet<String> set = new TreeSet<>(arbitraryNullFriendlyComparator());
                Collections.addAll(set, elements);
                return set;
              }
            })
        .named("TreeSet, with comparator")
        .withFeatures(

              @Override
              protected SortedMap<String, String> create(Entry<String, String>[] entries) {
                return populate(
                    new TreeMap<String, String>(arbitraryNullFriendlyComparator()), entries);
              }
            })
        .named("TreeMap, with comparator")
        .withFeatures(
            MapFeature.GENERAL_PURPOSE,
            MapFeature.ALLOWS_NULL_KEYS,