public void testImmutableCopy_empty() {
    assertThat(union(emptySet(), emptySet()).immutableCopy()).isEmpty();
    assertThat(intersection(newHashSet(1, 2), newHashSet(3, 4)).immutableCopy()).isEmpty();
    assertThat(difference(newHashSet(1, 2), newHashSet(1, 2)).immutableCopy()).isEmpty();
    assertThat(symmetricDifference(newHashSet(1, 2), newHashSet(1, 2)).immutableCopy()).isEmpty();
  }

  public void testImmutableCopy() {

                  : new MutatedOnQueryList<>(
                      transform(infiniteSetsFromStartIndex, ImmutableList::copyOf));
          Set<String> immutableCopy;
          try {
            immutableCopy = copyOf(input);
          } catch (RuntimeException e) {
            throw new RuntimeException(
                Strings.lenientFormat(