#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    int arr[n];
    for (int i = 0; i < n; i++) cin >> arr[i];
    sort(arr, arr + n);
    if (n == 2)
      cout << 0 << endl;
    else {
      if (arr[n - 2] > n - 2)
        cout << n - 2 << endl;
      else
        cout << arr[n - 2] - 1 << endl;
    }
  }
  return 0;
}
