.named("SafeTreeSet with natural comparator")
            .createTestSuite());
    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    NavigableSet<String> set = new SafeTreeSet<>(Ordering.natural().nullsFirst());

                        new SafeTreeSet<String>(asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingSortedSet[SafeTreeSet] with standard implementations")

                        new SafeTreeSet<String>(asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingNavigableSet[SafeTreeSet] with standard implementations")

                        new SafeTreeSet<String>(asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingSortedSet[SafeTreeSet] with standard implementations")

        NavigableSetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    SafeTreeSet<String> set = new SafeTreeSet<>(asList(elements));
                    return unmodifiableNavigableSet(set);
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {