#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <string>
#include <vector>
#include <cstdio>
#include <cassert>
#include <ctime>
#include <unordered_map>
#include <unordered_set>

using namespace std;

typedef long long ll;
typedef long double ld;

#ifdef WIN32
    #define LLD "%I64d"
#else
    #define LLD "%lld"
#endif

unordered_map<int, vector<int>> poss;
unordered_map<int, unordered_map<int, int>> was;

const int maxn = 1005;
char s[maxn][10];
int st27[10];
int len;

void add(char *s)
{
    int posmask = 0;
    for (int i = 0; i < len; i++) posmask |= (1 << (s[i] - 'A'));
    for (int mask = 0; mask < (1 << len); mask++)
    {
        int cur = 0;
        for (int i = 0; i < len; i++) cur = cur * 27 + ((mask & (1 << i)) ? 0 : s[i] - 'A' + 1);
        poss[cur].push_back(posmask);
    }
}

inline int get(int pos, int pl)
{
    return (pos / st27[pl]) % 27;
}

inline int set(int pos, int pl, int x)
{
    return pos + (x - (pos / st27[pl]) % 27) * st27[pl];
}

inline void printmask(int mask)
{
    for (int i = 0; i < 26; i++) if (mask & (1 << i)) cout << (char)('A' + i);
}

inline void printpos(int pos)
{
    for (int i = 0; i < len; i++)
    {
        if (pos % 27 == 0) cout << '?';
        else cout << (char)('A' + pos % 27 - 1);
        pos /= 27;
    }
}

bool go(int curpos, int nowmask, int delmask)
{
    if (__builtin_popcount(nowmask) == len) return false;
    auto whwas = was[curpos].find(delmask);
    if (whwas != was[curpos].end()) return whwas->second;
//  cout << "go ";
//  printmask(delmask);
//  cout << " ";
//  printpos(curpos);
//  cout << endl;
    bool can = false;
    for (auto x : poss[curpos]) can |= ((x & delmask) == 0);
//  if (!can) cout << "not found " << endl;
    if (!can)
    {
        was[curpos][delmask] = false;
        return false;
    }
    if (__builtin_popcount(delmask) > len)
    {
        was[curpos][delmask] = true;
        return true;
    }
    for (int c = 0; c < 26; c++) if (!((delmask | nowmask) & (1 << c)))
    {
        bool ok = go(curpos, nowmask, delmask | (1 << c));
        for (int pl = 0; pl < len && !ok; pl++) if (get(curpos, pl) == 0)
        {
            ok |= go(set(curpos, pl, c + 1), nowmask | (1 << c), delmask);
        }
        if (!ok)
        {
            was[curpos][delmask] = false;
            return false;
        }
    }
//  cout << "true ";
//  printmask(delmask);
//  cout << " ";
//  printpos(curpos);
//  cout << endl;
    was[curpos][delmask] = true;
    return true;
}

int main()
{
    st27[0] = 1;
    for (int i = 1; i <= 6; i++) st27[i] = st27[i - 1] * 27;
    int NT;
    scanf("%d", &NT);
    for (int T = 0; T < NT; T++)
    {
        int n;
        scanf("%d", &n);
        for (int i = 0; i < n; i++) scanf("%s", s[i]);
        bool ok = false;
        for (len = 1; len < 7; len++)
        {
//          cout << "len = " << len << endl;
            poss.clear();
            was.clear();
            for (int i = 0; i < n; i++) if ((int)strlen(s[i]) == len)
            {
                add(s[i]);
            }
//          cout << poss.size() << endl;
            if (go(0, 0, 0))
            {
                ok = true;
                printf("Yes\n");
                break;
            }
        }
        if (!ok) printf("No\n");
    }
    return 0;
}