#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t;
  cin >> t;
  while (t--) {
    long long n, m;
    cin >> n >> m;
    long long s = 0;
    for (long long i = 0; i < n; i++) {
      long long a;
      cin >> a;
      s += 2 * a;
    }
    if (n == m && n > 2) {
      cout << s << endl;
      for (long long i = 1; i < n; i++) cout << i << " " << i + 1 << endl;
      cout << n << " " << 1 << endl;
    } else
      cout << "-1\n";
  }
}
