#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n, i, sq, maxm = 0;
    cin >> n;
    int a[n];
    for (i = 0; i < n; i++) {
      cin >> a[i];
    }
    sort(a, a + n);
    for (i = 0; i < n; i++) {
      sq = min(a[i], (n - i));
      if (sq > maxm) {
        maxm = sq;
      }
    }
    cout << maxm << endl;
  }
  return 0;
}
