*       one with {@link CharSequence#charAt(int)}.
   *   <li>use {@link Appendable#append(CharSequence)} in {@link #copyTo(Appendable)} and {@link
   *       #copyTo(CharSink)}. We know this is correct since strings are immutable and so the length
   *       can't change, and it is faster because many writers and appendables are optimized for

    assertFalse(out.closed());
    source.copyTo(out);
    assertFalse(out.closed());
  }

  public void testClosesOnErrors_copyingToByteSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {
      TestByteSource okSource = new TestByteSource(bytes);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestByteSink(option)));

    assertFalse(out.closed());
    source.copyTo(out);
    assertFalse(out.closed());
  }

  public void testClosesOnErrors_copyingToByteSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {
      TestByteSource okSource = new TestByteSource(bytes);
      assertThrows(IOException.class, () -> okSource.copyTo(new TestByteSink(option)));

  private ListGenerators() {}

  public static class ImmutableListOfGenerator extends TestStringListGenerator {
    @Override
    protected List<String> create(String[] elements) {
      return ImmutableList.copyOf(elements);
    }
  }

  public static class BuilderAddListGenerator extends TestStringListGenerator {
    @Override
    protected List<String> create(String[] elements) {

    String[] array = new String[0];
    Multiset<String> multiset = ImmutableMultiset.copyOf(array);
    assertTrue(multiset.isEmpty());
  }

  public void testCreation_arrayOfOneElement() {
    String[] array = new String[] {"a"};
    Multiset<String> multiset = ImmutableMultiset.copyOf(array);
    assertEquals(HashMultiset.create(asList("a")), multiset);
  }

     */
    assertThat(ImmutableIntArray.copyOf(new int[0])).isSameInstanceAs(ImmutableIntArray.of());
  }

  public void testCopyOf_array_nonempty() {
    int[] array = new int[] {0, 1, 3};
    ImmutableIntArray iia = ImmutableIntArray.copyOf(array);
    array[2] = 2;
    assertThat(iia.asList()).containsExactly(0, 1, 3).inOrder();
  }

  public void testCopyOf_map_empty() {
    Map<Class<?>, Object> in = emptyMap();
    ClassToInstanceMap<Object> map = ImmutableClassToInstanceMap.copyOf(in);
    assertTrue(map.isEmpty());
    assertThat(map).isSameInstanceAs(ImmutableClassToInstanceMap.of());
    assertThat(ImmutableClassToInstanceMap.copyOf(map)).isSameInstanceAs(map);
  }

  public void testOf_zero() {
    assertTrue(ImmutableClassToInstanceMap.of().isEmpty());
  }

  }

  public void testCopyOf_arrayContainingOnlyNull() {
    @Nullable String[] array = new @Nullable String[] {null};
    assertThrows(NullPointerException.class, () -> ImmutableList.copyOf((String[]) array));
  }

  public void testCopyOf_collection_empty() {
    Collection<String> c = MinimalCollection.of();
    List<String> list = ImmutableList.copyOf(c);

  protected abstract <E extends Comparable<? super E>> Set<E> copyOf(E[] elements);

  protected abstract <E extends Comparable<? super E>> Set<E> copyOf(
      Collection<? extends E> elements);

  protected abstract <E extends Comparable<? super E>> Set<E> copyOf(
      Iterable<? extends E> elements);

  protected abstract <E extends Comparable<? super E>> Set<E> copyOf(
      Iterator<? extends E> elements);

        ImmutableBiMap.copyOf(Collections.<String, Integer>emptyMap());
    assertEquals(Collections.<String, Integer>emptyMap(), copy);
    assertThat(ImmutableBiMap.copyOf(copy)).isSameInstanceAs(copy);
    assertThat(copy).isSameInstanceAs(ImmutableBiMap.of());
  }

  public void testCopyOfSingletonMap() {
    ImmutableBiMap<String, Integer> copy = ImmutableBiMap.copyOf(singletonMap("one", 1));