#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <ctime>
#include <cmath>
#include <algorithm>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <list>
#include <set>
#include <map>

#define pb push_back
#define mp make_pair
#define TASKNAME ""

#ifdef DEBUG
#define eprintf(...) fprintf(stderr,__VA_ARGS__)
#else
#define eprintf(...)
#endif

#define TIMESTAMP(x) eprintf("[" #x "] Time = %.3lfs\n",clock()*1.0/CLOCKS_PER_SEC)

#ifdef _WIN32
#define LLD "%I64d"
#else
#define LLD "%lld"
#endif

#define sz(x) ((int)(x).size())
#define forn(i, n) for (int i = 0; i < (n); i++)

using namespace std;

typedef long double ld;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<int, ll> pil;
typedef pair<ll, ll> pll;
typedef vector<pii> vpii;

const int inf = 1e9;
const double eps = 1e-9;
const int INF = inf;
const double EPS = eps;

#ifdef DEBUG
struct __timestamper {
  ~__timestamper(){
    TIMESTAMP(end);
  }
} __Timestamper;
#else
struct __timestamper {};
#endif

/*Template end*/

int get_fixed(int msk, const string &w) {
  int res = 0;
  for (int i = 0; i < sz(w); i++) {
    if (msk & (1 << (w[i] - 'A'))) res |= 1 << i;
  }
  return res;
}

int len;
vector<string> ws;
map<pii, bool> cache;

bool calc(int msk, int id) {
  int fixed = get_fixed(msk, ws[id]);
  if (fixed == (1 << len) - 1) return false;
  {
    int bad = msk;
    forn (i, len)
      bad &= ~(1 << (ws[id][i] - 'A'));
    int bcnt = __builtin_popcount(bad);
    if (bcnt > len) return true;
  }

  if (cache.count(mp(msk, id))) return cache[mp(msk, id)];

  bool &res = cache[mp(msk, id)];
  res = true;
  for (int ne = 0; ne < 26; ne++) if (!(msk & (1 << ne))) {
    bool cres = false;
    for (int nid = 0; nid < sz(ws); nid++) {
      if (get_fixed(msk, ws[nid]) != fixed) continue;

      bool cok = true;
      forn (i, len) if (fixed & (1 << i)) {
        cok = cok && ws[nid][i] == ws[id][i];
      }
      if (cok) {
        cres = cres || calc(msk | (1 << ne), nid);
      }
    }
    res = res && cres;
  }
  return res;
}

bool solve() {
  assert(!ws.empty());
  len = sz(ws[0]);
  cache.clear();
  return calc(0, 0);
}

int main() {
  #ifdef DEBUG
  freopen(TASKNAME".in","r",stdin);
  #endif

  int TN;
  assert(scanf("%d", &TN) == 1);
  while (TN --> 0) {
    int n;
    scanf("%d", &n);
    map<int, vector<string> > aws;
    while (n --> 0) {
      char str[10];
      scanf("%s", str);
      aws[strlen(str)].pb(str);
    }
    bool ok = false;
    for (map<int, vector<string> >::const_iterator it = aws.begin(); it != aws.end(); it++) {
      ws = it->second;
      ok = ok || solve();
    }
    printf("%s\n", ok ? "Yes" : "No");
  }
  return 0;
}