public void testPollFirst() {
    assertEquals(a, navigableSet.pollFirst());
    assertEquals(values.subList(1, values.size()), copyToList(navigableSet));
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> navigableSet.pollFirst());
  }

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

        control.add(element);
        q.add(element);
      } else {
        assertEqualsUsingSeed(seed, control.poll(), q.pollFirst());
      }
    }
    while (!control.isEmpty()) {
      assertEqualsUsingSeed(seed, control.poll(), q.pollFirst());
    }
    assertTrue(q.isEmpty());
  }

  public void testExhaustive_pollAndPush() {
    int size = 5;

  public void testPollFirst() {
    assertEquals(a, navigableSet.pollFirst());
    assertEquals(values.subList(1, values.size()), copyToList(navigableSet));
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> navigableSet.pollFirst());
  }

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

    }
  }

  /**
   * Removes and returns the least element of this queue, or returns {@code null} if the queue is
   * empty.
   */
  @CanIgnoreReturnValue
  public @Nullable E pollFirst() {
    return poll();
  }

  /**
   * Removes and returns the least element of this queue.
   *
   * @throws NoSuchElementException if the queue is empty
   */
  @CanIgnoreReturnValue

    }
  }

  /**
   * Removes and returns the least element of this queue, or returns {@code null} if the queue is
   * empty.
   */
  @CanIgnoreReturnValue
  public @Nullable E pollFirst() {
    return poll();
  }

  /**
   * Removes and returns the least element of this queue.
   *
   * @throws NoSuchElementException if the queue is empty
   */
  @CanIgnoreReturnValue

        control.add(element);
        q.add(element);
      } else {
        assertEqualsUsingSeed(seed, control.poll(), q.pollFirst());
      }
    }
    while (!control.isEmpty()) {
      assertEqualsUsingSeed(seed, control.poll(), q.pollFirst());
    }
    assertTrue(q.isEmpty());
  }

  public void testExhaustive_pollAndPush() {
    int size = 5;

   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final @Nullable E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always

   */
  @CanIgnoreReturnValue
  @Deprecated
  @GwtIncompatible // NavigableSet
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final @Nullable E pollFirst() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the set unmodified.
   *
   * @since 12.0
   * @throws UnsupportedOperationException always

      return map().ceilingKey(e);
    }

    @Override
    public @Nullable K higher(@ParametricNullness K e) {
      return map().higherKey(e);
    }

    @Override
    public @Nullable K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    public @Nullable K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override

      return map().ceilingKey(e);
    }

    @Override
    public @Nullable K higher(@ParametricNullness K e) {
      return map().higherKey(e);
    }

    @Override
    public @Nullable K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    public @Nullable K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override