$rt$,

#include<bits/stdc++.h>
using namespace std;
int n;
int tree[10005][130],tot/*=1*/;
string a;
bool vis[100005];
bool pan(string s){
    int len=s.size(),u=1;
	bool flag=0;
    for(int i=0;i<len;i++){
        int x=s[i];
        if(!tree[u][x]) tree[u][x]=++tot;
        else if(i==len-1) flag=1;
        u=tree[u][x];
        if(vis[u])
			flag=1;
    }
    vis[u]=1;
    return flag;
}
void help(){
    memset(tree,0,sizeof(tree));
    memset(vis,0,sizeof(vis));
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a;
        if(pan(a)){
			cout<<"NO\n";
			return ;
		}
    }
	cout<<"YES\n";
	return ;
}
int main(){
	int t;
    cin>>t;
	while(t--)
		help();
	return 0;
}