型別：字典樹

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner kb = new Scanner(System.in);
        int t=kb.nextInt();
        while(t-->0) {
            int n=kb.nextInt();
            Trie trie=new Trie();
            boolean pd=true;
            String str1[]=new
 
 String[n]; 
            for(int i=0;i<n;i++){
                str1[i]=kb.next();
                trie.insert(str1[i]);
            }
            for(int i=0;i<n;i++){
                if(trie.countPrefix(str1[i])>1) {
                    pd=false;
                }
            }
            if
 
(pd)System.out.println("YES");
            else System.out.println("NO");
        }
        kb.close();
    }
}
class Trie{
    private int size=26;
    private TrieNode root;
    public Trie() {
        root=new TrieNode();
    }
    private class TrieNode{
        private int num;
        private TrieNode[] son;
        private
 
 boolean isEnd;
        private char val;
        public TrieNode() {
            num=1;
            son=new TrieNode[size];
            isEnd=false;
        }
    }
    public void insert(String str) {
        if(str==null||str.length()==0)return;
        TrieNode node=root;
        char letters[]=str.toCharArray();
        for(int i=0,len=str.length();i<len;i++) {
            int pos=letters[i]-'0';
            if(node.son[pos]==null) {
                node.son[pos]=new TrieNode();
                node.son[pos].val=letters[i];
            }else {
                node.son[pos].num++;
            }
            node=node.son[pos];
        }
        node.isEnd=true;
    }
    public int countPrefix(String prefix) {
        if(prefix==null||prefix.length()==0) {
            return -1;
        }
        TrieNode node=root;
        char[]letters=prefix.toCharArray();
        for(int i=0,len=prefix.length();i<len;i++) {
            int pos=letters[i]-'0';
            if(node.son[pos]==null)
                return 0;
            else
                node=node.son[pos];
        }
        return node.num;
    }
    public String hasPredix(String prefix) {
        if(prefix==null||prefix.length()==0) {
            return null;
        }
        TrieNode node=root;
        char[]letters=prefix.toCharArray();
        for(int i=0,len=prefix.length();i<len;i++) {
            int pos=letters[i]-'0';
            if(node.son[pos]==null)
                return null;
            else
                node=node.son[pos];
        }
        preTraverse(node,prefix);
        return prefix;
    }
    private void preTraverse(TrieNode node, String prefix) {
        if (!node.isEnd) {
            for (TrieNode child : node.son) {
                if (child != null) {
                    preTraverse(child, prefix + child.val);
                }
            }
            return;
        }
        System.out.println(prefix);
    }
}