Object newValue = new Object();
    valueRef.set(newValue);
    assertThat(cache.getIfPresent(new Object())).isSameInstanceAs(newValue);
  }

  public void testGetAllPresent_empty() {
    Cache<Object, Object> cache =
        new AbstractCache<Object, Object>() {
          @Override
          public @Nullable Object getIfPresent(Object key) {
            return null;
          }