/*
User ID: turing_13
Link: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2347
*/

#include <bits/stdc++.h>

#define pii pair <int,int>
#define sc scanf
#define pf printf
#define Pi 2*acos(0.0)
#define ms(a,b) memset(a, b, sizeof(a))
#define pb(a) push_back(a)
#define MP make_pair
#define oo 1<<29
#define dd double
#define ll long long
#define EPS 10E-10
#define ff first
#define ss second
#define MAX 10000
#define SZ(a) (int)a.size()
#define getint(a) scanf("%d",&a)
#define loop(i,n) for(int i=0;i<n;i++)
#define TEST_CASE(t) for(int z=1;z<=t;z++)
#define PRINT_CASE printf("Case %d:\n",z)
#define all(a) a.begin(),a.end()
#define intlim 2147483648
#define inf 1000000
#define rtintlim 46340
#define llim 9223372036854775808
#define rtllim 3037000499
#define ull unsigned long long
#define I int

using namespace std;

char data[20];
bool ans=0;

struct node
{
    bool endmark;
    node *ara[10];
    node()
    {
        endmark=0;
        for(int i=0; i<10; i++)
            ara[i]=NULL;
    }
}*root;

void insert(string str, int len)
{
    node *cur=root;
    for(int i=0;i<len;i++)
    {
        int indx=str[i]-'0';
        if(cur->ara[indx]==NULL)
            cur->ara[indx]=new node();
        cur=cur->ara[indx];
        if(cur->endmark)
                ans=1;
    }
    cur->endmark=1;
}


void del(node *cur)
{
    for(int i=0;i<10;i++)
    {
        if(cur->ara[i])
            del(cur->ara[i]);
    }
    delete (cur);
}

int main()
{
    ///freopen("in.txt","r",stdin);
    ///freopen("out.txt","w",stdout);
    int t;
    getint(t);
    vector<string>v;
    TEST_CASE(t)
    {
        root=new node();
        int n;
        getint(n);
        getchar();
        loop(i,n)
        {
            string str;
            cin>>str;
            v.pb(str);
        }
        sort(all(v));
        loop(i,n)
        {
            insert(v[i],SZ(v[i]));
        }
        if(ans)
            cout<<"NO\n";
        else
            cout<<"YES\n";
        ans=0;
        del(root);
        v.clear();
    }
    return 0;
}