#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

int main() {
    int T;
    cin >> T;
    assert(T <= 100000);
    assert(T >= 1);
    ll n_sum = 0;
    while (T--) {
        ll N, L;
        cin >> N >> L;
        assert(N >= 2);
        assert(L >= 1);
        assert(L <= 1000000000);

        vector<ll> X(N);
        vector<ll> Y(N);
        map<pll, ll> mp;
        for (ll i = 0; i < N; i++) {
            cin >> X[i] >> Y[i];
            assert(X[i] >= 0);
            assert(X[i] <= L);
            assert(Y[i] >= 0);
            assert(Y[i] <= L);
            assert(mp[pll(X[i], Y[i])] == 0);
            mp[pll(X[i], Y[i])]++;
        }
        ll width = L / 400;
        if (width == 0) {
            width = 1;
        }
        vector<vector<pll>> segs(402, vector<pll>(0));
        for (ll i = 0; i < N; i++) {
            ll x = X[i] / width;
            segs[x].push_back(pll(Y[i], X[i]));
        }
        for (ll i = 0; i <= 401; i++) {
            sort(all(segs[i]));
        }
        cout << N << endl;
        for (ll i = 0; i <= 401; i++) {
            for (ll j = 0; j < segs[i].size(); j++) {
                cout << segs[i][j].second << " " << segs[i][j].first << endl;
            }
        }
    }
}