// Ensure exceeding the low watermark does not make channel unwritable.
ch.write(buffer().writeZero(128));
assertThat(buf.toString(), is(""));
ch.unsafe().outboundBuffer().addFlush();
// Ensure exceeding the high watermark makes channel unwritable.
ch.write(buffer().writeZero(128));
assertThat(buf.toString(), is("false "));