r.mu.Lock()
	defer r.mu.Unlock()
	getDst := func(n int) []byte {
		if cap(dst) < n {
			return make([]byte, n)
		}
		return dst[:n]
	}

	if r.w == r.r {
		if r.isFull {
			buf := getDst(r.size)
			copy(buf, r.buf[r.r:])
			copy(buf[r.size-r.r:], r.buf[:r.w])
			return buf
		}
		return nil
	}

	if r.w > r.r {
		buf := getDst(r.w - r.r)
		copy(buf, r.buf[r.r:r.w])

    int index = aValidIndex();
    E initialValue = getList().get(index);
    assertEquals(
        "set(i, x) should return the old element at position i.",
        initialValue,
        getList().set(index, newValue));
    assertEquals("After set(i, x), get(i) should return x", newValue, getList().get(index));
    assertEquals("set() should not change the size of a list.", getNumElements(), getList().size());
  }

    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(moreElements)));
  }

  public void testEquals_list() {
    assertFalse("A List should never equal a Set.", getSet().equals(copyToList(getSet())));
  }

    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(moreElements)));
  }

  public void testEquals_list() {
    assertFalse("A List should never equal a Set.", getSet().equals(copyToList(getSet())));
  }

    private static class OptionComparator implements Comparator<Option> {
        @Override
        public int compare(Option opt1, Option opt2) {
            String s1 = opt1.getOpt() != null ? opt1.getOpt() : opt1.getLongOpt();
            String s2 = opt2.getOpt() != null ? opt2.getOpt() : opt2.getLongOpt();
            return s1.compareToIgnoreCase(s2);
        }
    }

    private static class CLIManagerExtension extends CLIManager {

  public void testSubList_startNegative() {
    assertThrows(IndexOutOfBoundsException.class, () -> getList().subList(-1, 0));
  }

  public void testSubList_endTooLarge() {
    assertThrows(IndexOutOfBoundsException.class, () -> getList().subList(0, getNumElements() + 1));
  }

  public void testSubList_startGreaterThanEnd() {
    try {
      getList().subList(1, 0);
      fail("subList(1, 0) should throw");

  public void testSubList_startNegative() {
    assertThrows(IndexOutOfBoundsException.class, () -> getList().subList(-1, 0));
  }

  public void testSubList_endTooLarge() {
    assertThrows(IndexOutOfBoundsException.class, () -> getList().subList(0, getNumElements() + 1));
  }

  public void testSubList_startGreaterThanEnd() {
    try {
      getList().subList(1, 0);
      fail("subList(1, 0) should throw");

   */
  public void testAddAtIndex_unsupportedPresent() {
    assertThrows(UnsupportedOperationException.class, () -> getList().add(0, e0()));
    expectUnchanged();
  }

  @ListFeature.Require(SUPPORTS_ADD_WITH_INDEX)
  public void testAddAtIndex_supportedNotPresent() {
    getList().add(0, e3());
    expectAdded(0, e3());
  }

  @CollectionFeature.Require(FAILS_FAST_ON_CONCURRENT_MODIFICATION)

    int index = aValidIndex();
    E initialValue = getList().get(index);
    assertEquals(
        "set(i, x) should return the old element at position i.",
        initialValue,
        getList().set(index, newValue));
    assertEquals("After set(i, x), get(i) should return x", newValue, getList().get(index));
    assertEquals("set() should not change the size of a list.", getNumElements(), getList().size());
  }

    assertFalse(
        "Lists of different sizes should not be equal.",
        getList().equals(new ArrayList<E>(moreElements)));
  }

  public void testEquals_set() {
    assertFalse("A List should never equal a Set.", getList().equals(MinimalSet.from(getList())));
  }