}

  public void testGetOnlyElement_withDefault_empty() {
    Iterable<String> iterable = emptyList();
    assertEquals("bar", getOnlyElement(iterable, "bar"));
  }

  public void testGetOnlyElement_withDefault_empty_null() {
    Iterable<String> iterable = emptyList();
    assertThat(Iterables.<@Nullable String>getOnlyElement(iterable, null)).isNull();
  }

  public void testGetOnlyElement_withDefault_multiple() {

  }

  public void testGetOnlyElement_withDefault_empty() {
    Iterator<String> iterator = emptyIterator();
    assertEquals("bar", getOnlyElement(iterator, "bar"));
  }

  public void testGetOnlyElement_withDefault_empty_null() {
    Iterator<String> iterator = emptyIterator();
    assertThat(Iterators.<@Nullable String>getOnlyElement(iterator, null)).isNull();
  }

  public void testGetOnlyElement_withDefault_two() {