private static <T extends @Nullable Object> Entry<T, T> entry(T key, T value) {
    return new AbstractMap.SimpleImmutableEntry<>(key, value);
  }

  public void testCopyOfMutableEntryList() {
    List<Entry<String, String>> entryList =
        Arrays.asList(
            new AbstractMap.SimpleEntry<>("a", "1"), new AbstractMap.SimpleEntry<>("b", "2"));
    ImmutableMap<String, String> map = ImmutableMap.copyOf(entryList);