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