assertTrue(set.containsAll(Sets.newTreeSet()));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("b"))));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "f"))));
    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));

    }
    assertTrue(
        SortedIterables.hasSameComparator(
            Ordering.natural().reverse(), Sets.newTreeSet(Ordering.natural().reverse())));
  }

  public void testComparator() {
    assertEquals(Ordering.natural(), SortedIterables.comparator(Sets.newTreeSet()));
  }

    }
    assertTrue(
        SortedIterables.hasSameComparator(
            Ordering.natural().reverse(), Sets.newTreeSet(Ordering.natural().reverse())));
  }

  public void testComparator() {
    assertEquals(Ordering.natural(), SortedIterables.comparator(Sets.newTreeSet()));
  }

                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .withFeatures(
                CollectionSize.ANY,
                CollectionFeature.KNOWN_ORDER,
                CollectionFeature.GENERAL_PURPOSE)

    verifySetContents(set, EMPTY_COLLECTION);
  }

  public void testNewTreeSetEmpty() {
    TreeSet<Integer> set = Sets.newTreeSet();
    verifySortedSetContents(set, EMPTY_COLLECTION, null);
  }

  public void testNewTreeSetEmptyDerived() {
    TreeSet<Derived> set = Sets.newTreeSet();
    assertTrue(set.isEmpty());
    set.add(new Derived("foo"));
    set.add(new Derived("bar"));

                  }

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

                  }

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

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Sets.newHashSet;
import static com.google.common.collect.Sets.newTreeSet;
import static com.google.common.collect.testing.SampleElements.Strings.AFTER_LAST;
import static com.google.common.collect.testing.SampleElements.Strings.AFTER_LAST_2;

                  }

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

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Sets.newHashSet;
import static com.google.common.collect.Sets.newTreeSet;
import static com.google.common.collect.testing.SampleElements.Strings.AFTER_LAST;
import static com.google.common.collect.testing.SampleElements.Strings.AFTER_LAST_2;