#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a,bool upp=0){if(a) cout<<(upp?"YES\n":"Yes\n"); else cout<<(upp?"NO\n":"No\n");}
template<class T> void vec_out(vector<T> &p,int ty=0){
if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}

namespace po167{
struct Mo{
	std::vector<int> left,right,order;
	int width,nl,nr,index,_n;
	Mo(int n):width((int) std::sqrt(n)),nl(0),nr(0),index(0),_n(0){}

	//[l,r)
	void insert(int l,int r){
		//assert(l<=r);
		left.push_back(l);
		right.push_back(r);
	}

	void bulid(){
		//width=(int)((double)_n/std::max((double)1,sqrt((int)(left.size()))));
		width=max(1,width);
		order.resize((int)left.size());
		std::vector<int> order1((int)left.size());
		std::iota(order1.begin(),order1.end(),0);
		auto order2=order1;
		std::sort(order1.begin(),order1.end(),[&](int a,int b){
			if(left[a]/width!=left[b]/width){
				return left[a]>left[b];
			}
			else if((left[a]/width)&1){
				return right[a]<right[b];
			}
			return right[a]>right[b];
		});
		std::sort(order2.begin(),order2.end(),[&](int a,int b){
			if((width/2+left[a])/width!=(width/2+left[b])/width){
				return left[a]>left[b];
			}
			else if(((width/2+left[a])/width)&1){
				return right[a]<right[b];
			}
			return right[a]>right[b];
		});
		ll score1=0,score2=0;
		for(int i=1;i<(int)(left.size());i++){
			score1+=std::abs(left[order1[i]]-left[order1[i-1]]);
			score1+=std::abs(right[order1[i]]-right[order1[i-1]]);
			score2+=std::abs(left[order2[i]]-left[order2[i-1]]);
			score2+=std::abs(right[order2[i]]-right[order2[i-1]]);
		}
		if(score1<score2) order=order1;
		else order=order2;
	}
	int process(){
		int now=order[index];
		//while(nr<right[now]) add(nr),nr++;
		//while(nl>left[now]) nl--,add(nl);
		//while(nl<left[now]) del(nl),nl++;
		//while(nr>right[now]) nr--,del(nr);
		index++;
		return now;
	}
};
}
using po167::Mo;


void solve();
// oddloop
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t=1;
    cin>>t;
    rep(i,0,t) solve();
}

void solve(){
    int N,L;
    cin>>N>>L;
    Mo X(L);
    vector<int> A(N),B(N);
    rep(i,0,N){
        int a,b;
        cin>>a>>b;
        A[i]=a,B[i]=b;
        X.insert(a,b);
    }
    X.bulid();
    cout<<N<<"\n";
    rep(i,0,N){
        int a=X.process();
        cout<<A[a]<<" "<<B[a]<<"\n";
    }
}