#include <bits/stdc++.h>

using namespace std;

string comp(string one, string other)
{
    bitset <1000> used{};
    sort(other.begin(), other.end(), greater<>());
    if(one >= other)
        return "-1";
    string ret = other, pref;
    reverse(other.begin(), other.end());
    int idx = 0;
    while(one.size() - idx)
    {
        int idx_eq = -1, idx_gr = -1;
        for(int i = 0; i < other.size(); i++)
        {
            if(!used[i])
            {
                if(other[i] == one[idx] && idx_eq == -1)
                    idx_eq = i;
                if(other[i] > one[idx] && idx_gr == -1)
                    idx_gr = i;
            }
            if(idx_eq != -1 && idx_gr != -1)
                break;
        }
        if(idx_gr != -1)
        {
            string chg = pref;
            chg += other[idx_gr];
            for(int i = 0; i < other.size(); i++)
                if(!used[i] && i != idx_gr)
                    chg += other[i];
            ret = min(ret, chg);
        }
        if(idx_eq != -1)
        {
            pref += one[idx];
            idx ++;
            used[idx_eq] = true;
        }
        else
            break;
    }
    if(!(one.size() - idx))
    {
        for(int i = 0; i < other.size(); i++)
            if(!used[i])
                pref += other[i];
        return pref;
    }
    else
        return ret;
}

int32_t main() {
    int q;
    cin >> q;
    while(q--)
    {
        int n;
        cin >> n;
        string prev;
        cin >> prev;
        sort(prev.begin(), prev.end());
        bool ok = true;
        while(n-- > 1)
        {
            string now;
            cin >> now;
            now = comp(prev, now);
            if(now == "-1")
            {
                ok = false;
                break;
            }
            prev = now;
        }
        cout << (ok ? "YES\n" : "NO\n");
    }
}