List<Integer> list1 = newArrayList(1);
    List<Integer> list2 = newArrayList(4);

    assertThrows(NullPointerException.class, () -> Iterables.concat(list1, null, list2));
  }

  public void testConcatPeformingFiniteCycle() {
    Iterable<Integer> iterable = asList(1, 2, 3);
    int n = 4;
    Iterable<Integer> repeated = Iterables.concat(nCopies(n, iterable));