#include <bits/stdc++.h> using namespace std; int t, n; bool flag; string s[10005]; int main() { cin >> t; while (t--) { flag = false; cin >> n; for (int i = 0; i < n; i++) { cin >> s[i]; } sort(s, s + n); for (int i = 0; i < n - 1; i++) { if (s[i + 1].substr(0, s[i].size()) == s[i]) { flag = true; break; } } cout << (flag ? "NO" : "YES") << endl; } return 0; }