return new Converter<String, String>(handleNullAutomatically) {
      @Override
      protected String doForward(String string) {
        return "forward";
      }

      @Override
      protected String doBackward(String string) {
        return "backward";
      }
    };
  }

  public void testSerialization_identity() {
    Converter<String, String> identityConverter = Converter.identity();

  protected abstract BiMap<String, String> create(Entry<String, String>[] entries);

  @Override
  @SuppressWarnings("unchecked")
  public final Entry<String, String>[] createArray(int length) {
    return (Entry<String, String>[]) new Entry<?, ?>[length];
  }

  @Override
  public final String[] createKeyArray(int length) {
    return new String[length];
  }

  @Override
  public final String[] createValueArray(int length) {

  public static class ImmutableSortedMapGenerator extends TestStringSortedMapGenerator {
    @Override
    public SortedMap<String, String> create(Entry<String, String>[] entries) {
      ImmutableSortedMap.Builder<String, String> builder = ImmutableSortedMap.naturalOrder();
      for (Entry<String, String> entry : entries) {
        checkNotNull(entry);
        builder.put(entry.getKey(), entry.getValue());
      }

    Set<String> set = of("a", "b", "c", "d", "e", "f", "g", "h");
    assertEquals(Sets.newHashSet("a", "b", "c", "d", "e", "f", "g", "h"), set);
  }

  public void testCopyOf_emptyArray() {
    String[] array = new String[0];
    Set<String> set = copyOf(array);
    assertEquals(Collections.<String>emptySet(), set);
    assertSame(this.<String>of(), set);
  }

  public void testCopyOf_arrayOfOneElement() {

    Set<String> set = of("a", "b", "c", "d", "e", "f", "g", "h");
    assertEquals(Sets.newHashSet("a", "b", "c", "d", "e", "f", "g", "h"), set);
  }

  public void testCopyOf_emptyArray() {
    String[] array = new String[0];
    Set<String> set = copyOf(array);
    assertEquals(Collections.<String>emptySet(), set);
    assertSame(this.<String>of(), set);
  }

  public void testCopyOf_arrayOfOneElement() {

    assertTrue(Arrays.equals(new String[] {"a"}, array));
  }

  @GwtIncompatible // Iterators.toArray(Iterator, Class)
  public void testToArray() {
    String[] sourceArray = new String[] {"a", "b", "c"};
    Iterator<String> iterator = asList(sourceArray).iterator();
    String[] newArray = Iterators.toArray(iterator, String.class);
    assertTrue(Arrays.equals(sourceArray, newArray));
  }

  public void copyOfImmutableNetwork_optimized() {
    Network<String, String> network1 =
        ImmutableNetwork.copyOf(NetworkBuilder.directed().<String, String>build());
    Network<String, String> network2 = ImmutableNetwork.copyOf(network1);

    assertThat(network2).isSameInstanceAs(network1);
  }

  @Test
  public void edgesConnecting_directed() {
    MutableNetwork<String, String> mutableNetwork =

            .<String>nodeOrder(ElementOrder.<String>natural());
    ImmutableValueGraph.Builder<String, Integer> immutableValueGraphBuilder =
        graphBuilder.<String, Integer>immutable();

    // Update ValueGraphBuilder, but this shouldn't impact immutableValueGraphBuilder
    graphBuilder.allowsSelfLoops(false).nodeOrder(ElementOrder.<String>unordered());

        Gender gender,
        Integer integer,
        int i,
        String string,
        CharSequence charSequence,
        List<String> list,
        ImmutableList<Integer> immutableList,
        Map<String, Integer> map,
        ImmutableMap<String, String> immutableMap,
        Set<String> set,
        ImmutableSet<Integer> immutableSet,
        SortedSet<Number> sortedSet,

  public static class ImmutableListMultimapGenerator extends TestStringListMultimapGenerator {
    @Override
    protected ListMultimap<String, String> create(Entry<String, String>[] entries) {
      ImmutableListMultimap.Builder<String, String> builder = ImmutableListMultimap.builder();
      for (Entry<String, String> entry : entries) {
        builder.put(entry.getKey(), entry.getValue());
      }
      return builder.build();
    }
  }