}

  public void testSerialization_empty() {
    assertThat(SerializableTester.reserialize(ImmutableClassToInstanceMap.of()))
        .isSameInstanceAs(ImmutableClassToInstanceMap.of());
  }

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