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;

        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;

        NavigableSet<Integer> filtered = filter(createUnfiltered(contents), EVEN);
        NavigableSet<Integer> unfiltered = createUnfiltered(filtered);

        assertEquals(unfiltered.pollFirst(), filtered.pollFirst());
        assertEquals(unfiltered, filtered);
      }
    }

    public void testPollLast() {
      for (List<Integer> contents : SAMPLE_INPUTS) {

    }
  }

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

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

    }
    try {
      unmod.addAll(singleton(4));
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.pollFirst();
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.pollLast();
      fail("UnsupportedOperationException expected");

    }
  }

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

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

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

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