.addEqualityGroup(integerToSpanish)
        .addEqualityGroup(Functions.compose(japaneseToInteger, integerToSpanish))
        .testEquals();
  }

  public void testCompositionWildcard() {
    Map<String, Integer> mapJapaneseToInteger = new HashMap<>();
    Function<String, Integer> japaneseToInteger = Functions.forMap(mapJapaneseToInteger);