let mut buf = Ringu::default();
    let mut push_count = 0;
    for i in 0..128 {
        push_count += buf.push_one(i as u8);
    }
    assert_eq!(push_count, 128);
    let mut read_count = 0;
    for i in 0..128) {
        let (nread, _val) = buf.read_one();
        read_count += nread;
    }   
    assert_eq!(read_count, 128);