### Question:
Iterables { public static <T> Iterable<T> concat(Iterable<? extends Iterable<? extends T>> iterables) { return com.google.common.collect.Iterables.concat(iterables); } private  Iterables(); static Iterable<T> concat(Iterable<? extends Iterable<? extends T>> iterables); static List<T> asList(Iterable<? extends T> iterable); static Set<T> asSet(Iterable<? extends T> iterable); static Multiset<T> asMultiset(Iterable<? extends T> iterable); static Collection<T> materialize(Iterable<? extends T> iterable); static Iterable<T> empty();  }### Answer:
@Test(expected = NullPointerException.class) public void shouldThrowANullPointerExceptionIfIterablePassedToConcatIsNull() throws Exception { concat(null); }