#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,s,n) for (int i = (s); i < (n); ++i)
#define rrep(i,g,n) for (int i = (n)-1; i >= (g); --i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define len(x) (int)(x).size()
#define dup(x,y) (((x)+(y)-1)/(y))
#define pb push_back
#define eb emplace_back
#define Field(T) vector<vector<T>>
using namespace std;
using ll = long long;
using ull = unsigned long long;
template<typename T> using pq = priority_queue<T,vector<T>,greater<T>>;
using P = pair<int,int>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}

void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  map<int,int> mp;
  rep(i,0,n) {
    cin >> a[i];
    ++mp[a[i]];
  }
  if (n == 1 && a[0] >= 2) {
    cout << a[0] << endl;
    return;
  }
  function<bool(int)> f = [&](int x) {
    int c0 = 0;
    for (auto [v, cnt] : mp) {
      if (v >= x) c0 += cnt;
    }
    ll val = 0;
    rrep(i,1,x) {
      int c = mp[i];
      if (val+1 <= c) {
        c0 += c-val-1;
      } else {
        val += (val+1-c);
        if (val >= 1000000000) return 0;
      }
      // cout << val << endl;
    }
    ++val;
    if (x) c0 += mp[0];
    if (val <= c0) return 1;
    return 0;
  };
  int ok = 0, ng = n+1;
  while(ng-ok > 1) {
    int mid = (ok+ng)/2;
    if (f(mid)) ok = mid;
    else ng = mid;
  }
  cout << ok << endl;
}

int main() {
  int t;
  cin >> t;
  while(t--) solve();
  return 0;
}