@Override
    public String toString() {
        String text = this.text;
        if (text == null) {
            // E.g.: "1000 Bye", "1009 Message too big"
            this.text = text = code() + " " + reasonText();
        }
        return text;
    }
@Test
    public void testToString() {
        assertEquals("1000 Bye", NORMAL_CLOSURE.toString());
    }