#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int i, n, f = 0;
    cin >> n;
    vector<int> v(n);
    vector<int> use(n + 1, 0);
    for (i = 0; i < n; i++) {
      cin >> v[i];
      if (v[i] < (i + 1)) {
        f = 1;
      }
    }
    if (f) {
      cout << "-1" << endl;
      continue;
    }
    vector<int> a(n, 0);
    for (i = 0; i < n; i++) {
      if (!use[v[i]]) {
        a[i] = v[i];
        use[v[i]] = 1;
      }
    }
    queue<int> q;
    for (i = 1; i <= n; i++) {
      if (!use[i]) {
        q.push(i);
      }
    }
    for (i = 0; i < n; i++) {
      if (a[i] != 0) {
        cout << a[i] << " ";
      } else {
        cout << q.front() << " ";
        q.pop();
      }
    }
    cout << endl;
  }
}
