return input.length();
    }
  }

  private static final Equivalence<String> LENGTH_EQUIVALENCE =
      Equivalence.equals().onResultOf(LengthFunction.INSTANCE);

  public void testWrap() {
    new EqualsTester()
        .addEqualityGroup(
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("world"))

      return input.length();
    }
  }

  private static final Equivalence<String> LENGTH_EQUIVALENCE =
      Equivalence.equals().onResultOf(LengthFunction.INSTANCE);

  public void testWrap() {
    new EqualsTester()
        .addEqualityGroup(
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("world"))

  public void testIsWrapperType() {
    assertThat(Primitives.isWrapperType(Void.class)).isTrue();
    assertThat(Primitives.isWrapperType(void.class)).isFalse();
  }

  public void testWrap() {
    assertThat(Primitives.wrap(int.class)).isSameInstanceAs(Integer.class);
    assertThat(Primitives.wrap(Integer.class)).isSameInstanceAs(Integer.class);

  public void testIsWrapperType() {
    assertThat(Primitives.isWrapperType(Void.class)).isTrue();
    assertThat(Primitives.isWrapperType(void.class)).isFalse();
  }

  public void testWrap() {
    assertThat(Primitives.wrap(int.class)).isSameInstanceAs(Integer.class);
    assertThat(Primitives.wrap(Integer.class)).isSameInstanceAs(Integer.class);

  }

  public void testRemove() {
    TestMap map = new TestMap();
    map.put("foo", 1);
    assertFalse(map.remove("foo", 2));
    assertFalse(map.remove("bar", 1));
    assertEquals(Integer.valueOf(1), map.get("foo"));
    assertTrue(map.remove("foo", 1));
    assertTrue(map.isEmpty());
  }

  public void testReplace() {
    TestMap map = new TestMap();
    map.put("foo", 1);

  }

  public void testRemove() {
    TestMap map = new TestMap();
    map.put("foo", 1);
    assertFalse(map.remove("foo", 2));
    assertFalse(map.remove("bar", 1));
    assertEquals(Integer.valueOf(1), map.get("foo"));
    assertTrue(map.remove("foo", 1));
    assertTrue(map.isEmpty());
  }

  public void testReplace() {
    TestMap map = new TestMap();
    map.put("foo", 1);

  protected <K, V> Map<K, V> create() {
    TestMap<K, V> inner = new TestMap<>(new HashMap<K, V>(), mutex);
    Map<K, V> outer = Synchronized.map(inner, mutex);
    return outer;
  }

  static class TestMap<K, V> extends ForwardingMap<K, V> implements Serializable {
    public final Object mutex;
    private Map<K, V> delegate;

    public TestMap(Map<K, V> delegate, Object mutex) {
      checkNotNull(mutex);

      return super.setValue(value);
    }

    private static final long serialVersionUID = 0;
  }

  static class TestMap<K, V> extends SynchronizedMapTest.TestMap<K, V>
      implements NavigableMap<K, V> {

    public TestMap(NavigableMap<K, V> delegate, Object mutex) {
      super(delegate, mutex);
    }

    @Override
    protected NavigableMap<K, V> delegate() {

  protected <K, V> Map<K, V> create() {
    TestMap<K, V> inner = new TestMap<>(new HashMap<K, V>(), mutex);
    Map<K, V> outer = Synchronized.map(inner, mutex);
    return outer;
  }

  static class TestMap<K, V> extends ForwardingMap<K, V> implements Serializable {
    public final Object mutex;
    private Map<K, V> delegate;

    public TestMap(Map<K, V> delegate, Object mutex) {
      checkNotNull(mutex);

      return super.setValue(value);
    }

    private static final long serialVersionUID = 0;
  }

  static class TestMap<K, V> extends SynchronizedMapTest.TestMap<K, V>
      implements NavigableMap<K, V> {

    public TestMap(NavigableMap<K, V> delegate, Object mutex) {
      super(delegate, mutex);
    }

    @Override
    protected NavigableMap<K, V> delegate() {