package Practice;

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.util.Arrays;

public class B5052 { //ÀüÈ­¹øÈ£ ¸ñ·Ï

public static void main(String[] args) throws Exception {

// TODO Auto-generated method stub

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

StringBuilder sb = new StringBuilder();

int T = Integer.parseInt(br.readLine());

Loop : while(T-- > 0) {

int N = Integer.parseInt(br.readLine());

String[] phone_book = new String[N];

for(int i = 0; i < N; i++) phone_book[i] = br.readLine();

Arrays.sort(phone_book);

for(int i = 1; i < N; i++) {

int len1 = phone_book[i - 1].length();

int len2 = phone_book[i].length();

if(len1 > len2 && phone_book[i - 1].substring(0, len2).equals(phone_book[i])) {

sb.append("NO\n");

continue Loop;

}

if(len1 <= len2 && phone_book[i].substring(0, len1).equals(phone_book[i - 1])){

sb.append("NO\n");

continue Loop;

}

}

sb.append("YES\n");

}

System.out.println(sb);

}

}