assertNotNull(ArbitraryInstances.get(Currency.class).getCurrencyCode());
    assertNotNull(ArbitraryInstances.get(Locale.class));
    assertNotNull(ArbitraryInstances.get(Joiner.class).join(ImmutableList.of("a")));
    assertNotNull(ArbitraryInstances.get(Splitter.class).split("a,b"));
    assertThat(ArbitraryInstances.get(com.google.common.base.Optional.class)).isAbsent();