#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

void solve()
{
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; ++i) cin >> a[i];
  for (int i = 0; i < n; ++i) if (a[i] >= n) a[i] = 0;
  int l = 0, r = n + 1;
  while (r - l > 1)
  {
    int mid = (l + r) / 2;
    vector<int> cnt(mid);
    for (int i = 0; i < n; ++i) ++cnt[(a[i] >= mid ? 1 : a[i])];
    int sum = 1, s0 = 0;
    for (int i = mid - 1; i > 0; --i)
    {
      int tmp = min(sum, cnt[i]);
      int val = sum - tmp;
      s0 += cnt[i] - tmp;
      sum += val;
      if (sum > n) sum = n + 1;
    }
    // cout << mid << ": " << (sum) << ',' << (cnt[0] + s0) << endl;
    (sum <= cnt[0] + s0 ? l : r) = mid;
  }
  cout << l << endl;
}

int main()
{
  int t;
  cin >> t;
  while (t--) solve();
}