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