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

using isize = size_t;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;
using f64 = long double;
using p2 = pair<i64, i64>;
using el = tuple<i64, i64, i64>;
using mint = atcoder::modint998244353;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}

i64 pow(i64 x, i64 n) {
  i64 res = 1;
  i64 t = x;
  while (n > 0) {
    if (n & 1) {
      res = res * t;
    }
    t = t * t;
    n >>= 1;
  }
  return res;
}
i64 pow(i64 x, i64 n, i64 m) {
  i64 res = 1;
  i64 t = x % m;
  while (n > 0) {
    if (n & 1) {
      res = res * t % m;
    }
    t = t * t % m;
    n >>= 1;
  }
  return res;
}

void _main() {
  i64 ttt;
  cin >> ttt;
  while (ttt--) {
    i64 n;
    cin >> n;
    i64 mx = -1;
    vector<pair<string, string>> xy(n);
    bool ok = false;
    for (i64 i = 0; i < n; i++) {
      string x, y;
      cin >> x >> y;
      xy[i] = {x, y};
      if (x != "a") continue;
      mx = max(mx, (i64)y.size());
      for (char c : y) {
        if (c == 'a') {
          ok = true;
          break;
        }
      }
    }
    bool e = false;
    bool b = false;
    for (auto [x, y] : xy) {
      bool all = true;
      for (char c : x) {
        if (c != 'b') all = false;
      }
      if (all && (i64)x.size() <= mx) b = true;
      bool f = false;
      for (char c : y) if (c == 'a') f = true;
      if (f && all) e = true;
    }
    if (ok || (b && e)) {
      cout << "Yes\n";
    } else {
      cout << "No\n";
    }
  }
}