#include <iostream>
#include <cstring>

using namespace std;

const int N = 100010;

int son[N][10], cnt[N], idx = 0;

void insert(string str){
    int p = 0;
    for (int i = 0; i < str.length(); i ++){
        int u = str[i] - '0';
        if (! son[p][u]) son[p][u] = ++ idx;
        p = son[p][u];
    }
    cnt[p] ++;
}

int query(string str){
    int p = 0;
    for (int i = 0; i < str.length(); i ++){
        int u = str[i] - '0';
        if (cnt[p]) return 1;
        p = son[p][u];
    }
    if (cnt[p] >= 2) return 1;
    return 0;
}

int main(){
    int t, n;
    scanf("%d", &t);
    while (t--){
        int n, flag = 0;
        scanf("%d", &n);
        memset(cnt, 0, sizeof cnt);
        memset(son, 0, sizeof son);
        idx = 0;
        string str[N];
        for (int i = 1; i <= n; i ++){
            cin >> str[i];
            insert(str[i]);
        }
        for (int i = 1; i <= n; i ++){
            if (query(str[i])) {
                flag = 1;
                break;
            }
        }
        cout<<(flag ? "NO": "YES")<<endl;
    }
}