#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int t;
    cin >> t;
    while(t--) {
        int n;
        cin >> n;
        bool ans = false;
        int cnt = 0;
        int mc = 1e9;
        map<string, string> mp;
        rep(i,n) {
            string x, y;
            cin >> x >> y;
            if(x=="a") {
                for(char c : y) if(c=='a' && y.size()>1) ans=true;
                if(!ans) {
                    mp[x] = max(mp[x], y);
                }
            }
            else{
                bool ex = true;
                for(char c : x) if(c=='a') ex = false;
                if(ex)  {
                    for(char c : y) if(c=='a') {
                        mp[x] = max(mp[x], y);                        
                    }
                }
            }
            
        }
        if(ans) {
            cout << "Yes" << endl;
        }
        else {
            string t = mp["a"];
            if(t=="" && t!="a") cout << "No" << endl;
            else{
                string r = mp[t];
                if(r!="") cout << "Yes" << endl;
                else{
                    bool f = false;
                    while(t.size()) {
                        t.pop_back();
                        string r = mp[t];
                        if(r!="") {
                            cout << "Yes" << endl;
                            f = true;
                            break;
                        }
                    }
                    if(!f) cout << "No" << endl;
                }
            }
        }
    }
    return 0;
}