SortedSet<String> set = of();
    assertThat(set.comparator()).isEqualTo(Ordering.natural());
  }

  public void testEmpty_headSet() {
    SortedSet<String> set = of();
    assertThat(set.headSet("c")).isSameInstanceAs(set);
  }

  public void testEmpty_tailSet() {
    SortedSet<String> set = of();
    assertThat(set.tailSet("f")).isSameInstanceAs(set);
  }

    Set<String> set = of("a", "b");
    assertEquals(newHashSet("a", "b"), set);
  }

  public void testCreation_threeElements() {
    Set<String> set = of("a", "b", "c");
    assertEquals(newHashSet("a", "b", "c"), set);
  }

  public void testCreation_fourElements() {
    Set<String> set = of("a", "b", "c", "d");
    assertEquals(newHashSet("a", "b", "c", "d"), set);
  }

  public void testCreation_fiveElements() {

    SortedSet<String> set = of();
    assertThat(set.comparator()).isEqualTo(Ordering.natural());
  }

  public void testEmpty_headSet() {
    SortedSet<String> set = of();
    assertThat(set.headSet("c")).isSameInstanceAs(set);
  }

  public void testEmpty_tailSet() {
    SortedSet<String> set = of();
    assertThat(set.tailSet("f")).isSameInstanceAs(set);
  }

    for (int i = 0; i < inputSize; i++) {
      builder.add(i % setSize);
    }
    ImmutableSet<Integer> set = builder.build();
    assertTrue(set instanceof RegularImmutableSet);
    assertEquals(
        "Input size " + inputSize + " and set size " + setSize,
        tableSize,
        ((RegularImmutableSet<Integer>) set).table.length);
  }

  public void testCopyOf_copiesImmutableSortedSet() {

    for (int i = 0; i < inputSize; i++) {
      builder.add(i % setSize);
    }
    ImmutableSet<Integer> set = builder.build();
    assertTrue(set instanceof RegularImmutableSet);
    assertEquals(
        "Input size " + inputSize + " and set size " + setSize,
        tableSize,
        ((RegularImmutableSet<Integer>) set).table.length);
  }

  public void testCopyOf_copiesImmutableSortedSet() {

   */
  private Iterable<List<Object>> buildCartesianProduct(Set<?>... sets) {
    List<Set<Optional<?>>> optionalSets = Lists.newArrayListWithExpectedSize(sets.length);
    for (Set<?> set : sets) {
      Set<Optional<?>> optionalSet =
          Sets.newLinkedHashSet(Iterables.transform(set, Optional::fromNullable));
      optionalSets.add(optionalSet);
    }
    Set<List<Optional<?>>> cartesianProduct = Sets.cartesianProduct(optionalSets);

  /**
   * Returns a {@link Set} whose methods throw {@link IllegalStateException} when the given node is
   * not present in this network.
   *
   * @since 33.1.0
   */
  protected final <T> Set<T> nodeInvalidatableSet(Set<T> set, N node) {
    return InvalidatableSet.of(
        set, () -> nodes().contains(node), () -> String.format(NODE_REMOVED_FROM_GRAPH, node));
  }

  /**

        // Verify all array elements are in Set
        for (String field : queryFieldConfig.searchFields) {
            assertTrue("Search field " + field + " should be in Set", queryFieldConfig.searchFieldSet.contains(field));
        }
        for (String field : queryFieldConfig.facetFields) {
            assertTrue("Facet field " + field + " should be in Set", queryFieldConfig.facetFieldSet.contains(field));
        }

        Set<String> roleSet = new HashSet<>();
        roleQueryHelperImpl.processHeader(request, roleSet);
        return roleSet;
    }

    private Set<String> buildByCookie(final RoleQueryHelper roleQueryHelperImpl, final HttpServletRequest request) {
        Set<String> roleSet = new HashSet<>();
        roleQueryHelperImpl.processCookie(request, roleSet);
        return roleSet;
    }

  }

  public void testFrequency_set() {
    Set<String> set = newHashSet("a", "b", "c");
    assertEquals(1, frequency(set, "a"));
    assertEquals(1, frequency(set, "b"));
    assertEquals(1, frequency(set, "c"));
    assertEquals(0, frequency(set, "d"));
    assertEquals(0, frequency(set, 4.2));
    assertEquals(0, frequency(set, null));
  }

  public void testFrequency_list() {