@Test
 public void shouldReturnReadOnlyDerivedBuffer() {
   ByteBuf buf = Unpooled.unmodifiableBuffer(Unpooled.buffer(1));
   assertTrue(buf.duplicate() instanceof ReadOnlyByteBuf);
   assertTrue(buf.slice() instanceof ReadOnlyByteBuf);
   assertTrue(buf.slice(0, 1) instanceof ReadOnlyByteBuf);
   assertTrue(buf.duplicate() instanceof ReadOnlyByteBuf);
 }