int n = 4;
    Iterable<Integer> repeated = Iterables.concat(nCopies(n, iterable));
    assertThat(repeated).containsExactly(1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3).inOrder();
  }

  public void testPartition_badSize() {
    Iterable<Integer> source = singleton(1);
    assertThrows(IllegalArgumentException.class, () -> Iterables.partition(source, 0));
  }

  public void testPartition_empty() {

    a = emptySet();
    b = asList(4, 8, 15, 16, 23, 42);
    assertFalse(elementsEqual(a.iterator(), b.iterator()));
    assertFalse(elementsEqual(b.iterator(), a.iterator()));
  }

  public void testPartition_badSize() {
    Iterator<Integer> source = singletonIterator(1);
    assertThrows(IllegalArgumentException.class, () -> Iterators.partition(source, 0));
  }

  public void testPartition_empty() {