assertTrue(map.isEmpty());
    assertThat(map).isSameInstanceAs(ImmutableClassToInstanceMap.of());
    assertThat(ImmutableClassToInstanceMap.copyOf(map)).isSameInstanceAs(map);
  }

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

  public void testOf_one() {
    ImmutableClassToInstanceMap<Number> map = ImmutableClassToInstanceMap.of(int.class, 1);