/* Test that it can be empty. */
    EnumBiMap<Currency, Country> emptyBimap = EnumBiMap.create(Currency.class, Country.class);
    EnumBiMap<Currency, Country> bimap3 = EnumBiMap.create(emptyBimap);
    assertEquals(bimap3, emptyBimap);
  }

  @GwtIncompatible // keyType
  public void testKeyType() {
    EnumBiMap<Currency, Country> bimap = EnumBiMap.create(Currency.class, Country.class);

    Map<Currency, String> emptyBimap = EnumHashBiMap.create(Currency.class);
    bimap = EnumHashBiMap.create(emptyBimap);
    assertTrue(bimap.isEmpty());

    /* Map can be empty if it's an EnumBiMap. */
    Map<Currency, Country> emptyBimap2 = EnumBiMap.create(Currency.class, Country.class);
    EnumHashBiMap<Currency, Country> bimap2 = EnumHashBiMap.create(emptyBimap2);
    assertTrue(bimap2.isEmpty());
  }

    Map<Currency, String> emptyBimap = EnumHashBiMap.create(Currency.class);
    bimap = EnumHashBiMap.create(emptyBimap);
    assertTrue(bimap.isEmpty());

    /* Map can be empty if it's an EnumBiMap. */
    Map<Currency, Country> emptyBimap2 = EnumBiMap.create(Currency.class, Country.class);
    EnumHashBiMap<Currency, Country> bimap2 = EnumHashBiMap.create(emptyBimap2);
    assertTrue(bimap2.isEmpty());
  }