#include <iostream>
#include <cstring>
#include <string>
#include <algorithm>
using namespace std;

struct Node{
    Node* pt[10];
    bool isEnd;
};
Node* root;

int n;
string s[10005];
Node memory[100000];
int allo;

void trie_init()
{
    memset(memory, 0, sizeof(memory));
    allo = 0;
    root = &memory[allo++];
}

bool trie_insert(string& str)
{
    Node *p = root, *q;
    for(int i = 0; str[i] != ‘\0‘; ++i){
        int id = str[i]-‘0‘;
        if(p->pt[id] == NULL){
            q = &memory[allo++];
            p->pt[id] = q;
        }
        else{
            if(p->pt[id]->isEnd)
                return false;
        }
        p = p->pt[id];
    }
    p->isEnd = true;
    return true;
}

void solve()
{
    trie_init();
    bool ok = true;
    for(int i = 0; i < n; ++i){
        ok = trie_insert(s[i]);
        if(!ok){
            cout<<"NO"<<endl;
            return;
        }
    }
    cout<<"YES"<<endl;
}

bool cmp(const string& a, const string& b)
{
    return a.length() < b.length();
}

int main()
{
    int t;
    cin>>t;
    while(t--){
        cin>>n;
        for(int i = 0; i < n; ++i)
            cin>>s[i];
        sort(s, s+n, cmp);
        solve();
    }
    return 0;
}