assertThat(FluentIterable.from(sortedSet).first()).isAbsent();
  }

  public void testFirst_iterable() {
    Set<String> set = ImmutableSet.of("a", "b", "c");
    assertThat(FluentIterable.from(set).first()).hasValue("a");
  }

  public void testFirst_emptyIterable() {
    Set<String> set = newHashSet();
    assertThat(FluentIterable.from(set).first()).isAbsent();
  }

  public void testLast_list() {

      Path dir = fs.getPath("dir");
      Files.createDirectory(dir);

      ByteSource source = MoreFiles.asByteSource(dir);

      assertThat(source.sizeIfKnown()).isAbsent();

      assertThrows(IOException.class, () -> source.size());
    }
  }

  public void testByteSource_size_ofSymlinkToDirectory() throws IOException {

    assertThat(tryFind(list, equalTo("pants"))).hasValue("pants");
    assertThat(tryFind(list, Predicates.alwaysTrue())).hasValue("cool");
    assertThat(tryFind(list, Predicates.alwaysFalse())).isAbsent();
    assertCanIterateAgain(list);
  }

  private static class TypeA {}

  private interface TypeB {}

  private static class HasBoth extends TypeA implements TypeB {}

  public void testTryFind_alwaysFalse_isPresent() {
    Iterable<String> list = Lists.newArrayList("cool", "pants");
    Iterator<String> iterator = list.iterator();
    assertThat(tryFind(iterator, Predicates.alwaysFalse())).isAbsent();
    assertFalse(iterator.hasNext());
  }

  public void testTransform() {
    Iterator<String> input = asList("1", "2", "3").iterator();
    Iterator<Integer> result =
        Iterators.transform(

  public void testTryFind_alwaysFalse_isPresent() {
    Iterable<String> list = Lists.newArrayList("cool", "pants");
    Iterator<String> iterator = list.iterator();
    assertThat(tryFind(iterator, Predicates.alwaysFalse())).isAbsent();
    assertFalse(iterator.hasNext());
  }

  public void testTransform() {
    Iterator<String> input = asList("1", "2", "3").iterator();
    Iterator<Integer> result =
        Iterators.transform(