mod util {
    pub trait Join {
        fn join(self, sep: &str) -> String;
    }

    impl<T, I> Join for I
    where
        I: Iterator<Item = T>,
        T: std::fmt::Display,
    {
        fn join(self, sep: &str) -> String {
            let mut s = String::new();
            use std::fmt::*;
            for (i, v) in self.enumerate() {
                if i > 0 {
                    write!(&mut s, "{}", sep).ok();
                }
                write!(&mut s, "{}", v).ok();
            }
            s
        }
    }
}
// ---------- begin scannner ----------
#[allow(dead_code)]
mod scanner {
    use std::str::FromStr;
    pub struct Scanner<'a> {
        it: std::str::SplitWhitespace<'a>,
    }
    impl<'a> Scanner<'a> {
        pub fn new(s: &'a String) -> Scanner<'a> {
            Scanner {
                it: s.split_whitespace(),
            }
        }
        pub fn next<T: FromStr>(&mut self) -> T {
            self.it.next().unwrap().parse::<T>().ok().unwrap()
        }
        pub fn next_bytes(&mut self) -> Vec<u8> {
            self.it.next().unwrap().bytes().collect()
        }
        pub fn next_chars(&mut self) -> Vec<char> {
            self.it.next().unwrap().chars().collect()
        }
        pub fn next_vec<T: FromStr>(&mut self, len: usize) -> Vec<T> {
            (0..len).map(|_| self.next()).collect()
        }
    }
}
// ---------- end scannner ----------

use std::collections::*;
use std::io::Write;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

fn main() {
    use std::io::Read;
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut sc = scanner::Scanner::new(&s);
    let out = std::io::stdout();
    let mut out = std::io::BufWriter::new(out.lock());
    run(&mut sc, &mut out);
}

fn run<W: Write>(sc: &mut scanner::Scanner, out: &mut std::io::BufWriter<W>) {
    let t: u32 = sc.next();
    for _ in 0..t {
        let n: usize = sc.next();
        let mut e = vec![vec![]; n];
        for e in e.iter_mut() {
            let m = sc.next::<usize>();
            e.resize(m, 0usize);
            for e in e.iter_mut() {
                *e = sc.next::<usize>() - 1;
            }
        }
        let (q, ans) = solve(e);
        writeln!(out, "{}", q).ok();
        for (f, a) in ans {
            use util::*;
            writeln!(out, "{} {}", f + 1, a.iter().map(|a| *a + 1).join(" ")).ok();
        }
    }
}

fn solve(e: Vec<Vec<usize>>) -> (usize, Vec<(usize, Vec<usize>)>) {
    let n = e.len();
    let mut list = vec![vec![]; n - 1];
    for (i, e) in e.iter().enumerate() {
        for e in e.iter() {
            list[*e].push(i);
        }
    }
    let deg = e.iter().map(|e| e.len()).collect::<Vec<_>>();
    let mut q = (1..).find(|&p| p * p >= 2 * (n - 1)).unwrap().max(*deg.iter().max().unwrap());
    if greedy(&deg, q).is_none() {
        q += 1;
    }
    assert!(greedy(&deg, q).is_some());
    (0, vec![])
}

fn greedy(a: &[usize], q: usize) -> Option<Vec<usize>> {
    let n = a.len();
    assert!(a.iter().sum::<usize>() == 2 * (n - 1));
    let mut rem = vec![q; q];
    let mut h = std::collections::BinaryHeap::new();
    for i in 0..q {
        h.push((q, i));
    }
    let mut ans = vec![0; n];
    let mut ord = (0..n).collect::<Vec<_>>();
    ord.sort_by_key(|v| a[*v]);
    for x in ord.into_iter().rev() {
        let a = a[x];
        let ans = &mut ans[x];
        let (_, k) = h.pop().unwrap();
        if rem[k] < a {
            return None;
        }
        *ans = k;
        rem[k] -= a;
        h.push((rem[k], k));
    }
    Some(ans)
}