#include <bits/stdc++.h>
using namespace std;

using Int = long long;
const char newl = '\n';

template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}
template<typename T> void drop(const T &x){cout<<x<<endl;exit(0);}
template<typename T=int>
vector<T> read(size_t n){
  vector<T> ts(n);
  for(size_t i=0;i<n;i++) cin>>ts[i];
  return ts;
}

//INSERT ABOVE HERE
signed solve(){
  int n;
  cin>>n;
  map<string, set<int>> mp;
  for(int i=0;i<n;i++){
    string c;
    int d;
    cin>>c>>d;
    mp[c].emplace(d);
  }
  vector<string> ks;
  for(auto&[k,v]:mp) ks.emplace_back(k);
  sort(ks.begin(),ks.end());

  if(ks.size()==1){
    cout<<"YES"<<newl;
    return 0;
  }

  int ok=0;
  do{
    int ng=0;
    auto cur=mp[ks[0]];
    for(int i=1;i<(int)ks.size();i++){
      auto nxt=mp[ks[i]];
      set<int> intersection;
      for(int l:cur)
        if(nxt.count(l))
          intersection.emplace(l);

      if(intersection.size()==0){
        ng=1;
        break;
      }

      if(intersection.size()==1){
        if(nxt.size()!=1){
          nxt.erase(*intersection.begin());
        }
        cur=nxt;
        continue;
      }

      cur=nxt;
    }
    if(!ng) ok=1;
  }while(next_permutation(ks.begin(),ks.end()));
  cout<<(ok?"YES":"NO")<<newl;
  return 0;
}

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(0);

  int t;
  cin>>t;
  while(t--) solve();

  return 0;
}