@Override
    public ByteBuf duplicate() {
        ensureAccessible();
        return new UnpooledDuplicatedByteBuf(this);
    }
@Test
    public void testDuplicateAfterRelease() {
        assertThrows(IllegalReferenceCountException.class, new Executable() {
            @Override
            public void execute() {
                releasedBuffer().duplicate();
            }
        });
    }