// 12 7
// by qiu
// funtion trie
#include <cstdio>
#include <cstdlib>
#include <malloc.h>
#include <cstring>
typedef struct node{
    int val;
    struct node *next[10];
}tree;
tree *build(){
            tree *root=(tree*)malloc(sizeof(node));
            root->val=1;
            for(int i=0; i<10; i++)
                     root->next[i]=NULL;
           return root;
}
void insert_tree(tree *root, char *s){
              int i=0;
              while(s[i]){
                    int k=s[i]-'0';
                    if(!root->next[k])
                              root->next[k]=build();
                    else
                              root->next[k]->val++;

                    root=root->next[k];
                    i++;

              }
}
int search_tree(tree *root, char *s){
           int cnt=0, i=0;
          while(s[i]){
                    int k=s[i]-'0';
                    if(!root->next[k])
                               return 0;
                    cnt=root->next[k]->val;
                    root=root->next[k];
                    i++;
            }
            return cnt;
}
void Delete(tree *T){
            if(T==NULL)
                    return;
          for(int i=0; i<10; i++)
                    if(T->next[i]!=NULL)
                            Delete(T->next[i]);
          free(T);
          return ;

}
int main(){
            int t, n, i;
            char s[10010][11];
            scanf("%d", &t);
            while(t--){
          scanf("%d", &n);
           tree *Root=build();
          for(i=0; i<n; i++){
                    scanf("%s", s[i]);
                    insert_tree(Root, s[i]);
           }
            for(i=0; i<n; i++){
            if(search_tree(Root, s[i])>1)
                    break;

           }
          if(i>=n)
                    printf("YES\n");
          else
                    printf("NO\n");
                    Delete(Root);

    }
   return 0;
}