#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*, BufWriter, StdinLock, StdoutLock};
use std::str;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let t = input!(usize);

    for _ in 0..t {
        solve(&mut scan, &mut out);
    }
}

fn solve(scan: &mut Scanner<StdinLock>, out: &mut BufWriter<StdoutLock>) {
    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let N = input!(usize);
    let L = input!(usize);

    let mut P = vec![];

    let mut Sxy = std::collections::BTreeSet::new();
    let mut Syx = std::collections::BTreeSet::new();

    let dist =
        |p1: (isize, isize), p2: (isize, isize)| return (p1.0 - p2.0).abs() + (p1.1 - p2.1).abs();

    for _ in 0..N {
        let (x, y) = (input!(isize), input!(isize));
        P.push((x, y));
        Sxy.insert((x, y));
        Syx.insert((y, x));
    }

    let (x, y) = P[0];
    Sxy.remove(&(x, y));
    Syx.remove(&(y, x));

    let mut route = vec![P[0]];
    let mut now = P[0];

    while !Sxy.is_empty() {
        let mut cand = vec![];

        let nxt = Sxy.range(..now).next_back();
        if let Some(&p) = nxt {
            cand.push(p);
        }

        let nxt = Sxy.range(now..).next();
        if let Some(&p) = nxt {
            cand.push(p);
        }

        let now_inv = (now.1, now.0);

        let nxt = Syx.range(..now_inv).next_back();
        if let Some(&p) = nxt {
            cand.push((p.1, p.0));
        }

        let nxt = Syx.range(now_inv..).next();
        if let Some(&p) = nxt {
            cand.push((p.1, p.0));
        }

        cand.sort_by_key(|&p| dist(p, now));

        let nxt = cand[0];

        route.push(nxt);
        now = nxt;

        Sxy.remove(&now);
        Syx.remove(&(now.1, now.0));
    }

    writeln!(out, "{}", route.len());

    for (x, y) in route {
        writeln!(out, "{} {}", x, y);
    }
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}