* testing. At that point, we may be able to eliminate the "hole" tests, which would mean that
   * ContiguousSet's tests would no longer need to suppress them.
   */
  @CollectionSize.Require(SEVERAL)
  public void testLower() {
    assertEquals(null, navigableSet.lower(a));
    assertEquals(a, navigableSet.lower(b));
    assertEquals(b, navigableSet.lower(c));
  }

  @CollectionSize.Require(SEVERAL)
  public void testFloor() {

   * testing. At that point, we may be able to eliminate the "hole" tests, which would mean that
   * ContiguousSet's tests would no longer need to suppress them.
   */
  @CollectionSize.Require(SEVERAL)
  public void testLower() {
    assertEquals(null, navigableSet.lower(a));
    assertEquals(a, navigableSet.lower(b));
    assertEquals(b, navigableSet.lower(c));
  }

  @CollectionSize.Require(SEVERAL)
  public void testFloor() {

  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> navigableMap.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLower() {
    resetWithHole();
    assertEquals(null, navigableMap.lowerEntry(a.getKey()));
    assertEquals(null, navigableMap.lowerKey(a.getKey()));
    assertEquals(a, navigableMap.lowerEntry(b.getKey()));

  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> sortedMultiset.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLower() {
    resetWithHole();
    assertEquals(null, sortedMultiset.headMultiset(a.getElement(), OPEN).lastEntry());
    assertEquals(a, sortedMultiset.headMultiset(b.getElement(), OPEN).lastEntry());

  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> sortedMultiset.pollFirstEntry());
  }

  @CollectionSize.Require(SEVERAL)
  public void testLower() {
    resetWithHole();
    assertEquals(null, sortedMultiset.headMultiset(a.getElement(), OPEN).lastEntry());
    assertEquals(a, sortedMultiset.headMultiset(b.getElement(), OPEN).lastEntry());