Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(1, powerSet.size());
    assertEquals(ImmutableSet.of(ImmutableSet.of()), powerSet);
    assertEquals(0, powerSet.hashCode());
  }

  public void testPowerSetContents() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(8, powerSet.size());

    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(1, powerSet.size());
    assertEquals(ImmutableSet.of(ImmutableSet.of()), powerSet);
    assertEquals(0, powerSet.hashCode());
  }

  public void testPowerSetContents() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(8, powerSet.size());

import java.util.Set;

/**
 * Very simple powerSet iteration benchmark.
 *
 * @author Kevin Bourrillion
 */
public class PowerSetBenchmark {
  @Param({"2", "4", "8", "16"})
  int elements;

  Set<Set<Integer>> powerSet;

  @BeforeExperiment
  void setUp() {
    Set<Integer> set = ContiguousSet.create(Range.closed(1, elements), integers());
    powerSet = Sets.powerSet(set);
  }

  @Benchmark

import java.util.Set;

/**
 * Very simple powerSet iteration benchmark.
 *
 * @author Kevin Bourrillion
 */
public class PowerSetBenchmark {
  @Param({"2", "4", "8", "16"})
  int elements;

  Set<Set<Integer>> powerSet;

  @BeforeExperiment
  void setUp() {
    Set<Integer> set = ContiguousSet.create(Range.closed(1, elements), integers());
    powerSet = Sets.powerSet(set);
  }

  @Benchmark

  public void testContainsAll() {
    ImmutableSortedSet<Integer> set = ContiguousSet.create(Range.closed(1, 3), integers());
    for (Set<Integer> subset : Sets.powerSet(ImmutableSet.of(1, 2, 3))) {
      assertTrue(set.containsAll(subset));
    }
    for (Set<Integer> subset : Sets.powerSet(ImmutableSet.of(1, 2, 3))) {
      assertFalse(set.containsAll(Sets.union(subset, ImmutableSet.of(9))));
    }

  public void testContainsAll() {
    ImmutableSortedSet<Integer> set = ContiguousSet.create(Range.closed(1, 3), integers());
    for (Set<Integer> subset : Sets.powerSet(ImmutableSet.of(1, 2, 3))) {
      assertTrue(set.containsAll(subset));
    }
    for (Set<Integer> subset : Sets.powerSet(ImmutableSet.of(1, 2, 3))) {
      assertFalse(set.containsAll(Sets.union(subset, ImmutableSet.of(9))));
    }

        return inputSet.keySet().containsAll(set);
      }
      return false;
    }

    @Override
    public boolean equals(@CheckForNull Object obj) {
      if (obj instanceof PowerSet) {
        PowerSet<?> that = (PowerSet<?>) obj;
        return inputSet.keySet().equals(that.inputSet.keySet());
      }
      return super.equals(obj);
    }

    @Override
    public int hashCode() {
      /*

            Range.closed(4, 6),
            Range.closedOpen(1, 3),
            Range.openClosed(5, 7),
            Range.open(3, 4));
    subsets:
    for (Set<Range<Integer>> subset : Sets.powerSet(ranges)) {
      assertEquals(TreeRangeSet.create(subset), ImmutableRangeSet.unionOf(subset));

      RangeSet<Integer> mutable = TreeRangeSet.create();

            Range.closed(4, 6),
            Range.closedOpen(1, 3),
            Range.openClosed(5, 7),
            Range.open(3, 4));
    subsets:
    for (Set<Range<Integer>> subset : Sets.powerSet(ranges)) {
      assertEquals(TreeRangeSet.create(subset), ImmutableRangeSet.unionOf(subset));

      RangeSet<Integer> mutable = TreeRangeSet.create();