problem f

#include<bits/stdc++.h>
using namespace std;
#define fast_io ios::sync_with_stdio(0); cout.tie(NULL); cin.tie(NULL)
#define ll long long
#define ull unsigned long long
#define pii pait<int, int>
#define sp(x) cout<<x<<' '
#define el(x) cout<<x<<endl
#define pb push_back
#define fi first
#define se second
const int mod = 1e9+7;

bool check(pair<string, int> &a, pair<string, int> &b){
    if(a.se > b.se) return true;
    if(a.se < b.se) return false;
    if(a.fi < b.fi) return true;
    return false;
}

void solve(){
    map<string, int> m;
    int n; cin>>n;
    string s;
    int a;
    for(int i=0; i<n; i++){
        cin>>s>>a;
        m[s]+=a;
    }
    vector<pair<string, int>> v;
    for(auto x:m){
        v.pb({x.fi, x.se});
    }
    sort(v.begin(), v.end(), check);
    cout<<v.size()<<endl;
    for(int i=0; i<v.size(); i++){
        cout<<v[i].fi<<' '<<v[i].se<<endl;
    }
}

int main(){
    fast_io;
    int t; cin>>t;
    while(t--) solve();
}