#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    string s[n];
    unordered_map<string, int> mp;
    int count = 0;
    for (int i = 0; i < n; i++) {
      cin >> s[i];
      mp[s[i]] += 1;
    }
    for (int i = 0; i < n; i++) {
      if (mp[s[i]] > 1) {
        count += 1;
        mp[s[i]] -= 1;
        for (int j = 0; j < 10; j++) {
          string s1 = s[i];
          s1[3] = '0' + j;
          if (mp[s1] == 0) {
            mp[s1] += 1;
            s[i] = s1;
            break;
          }
        }
      }
    }
    cout << count << endl;
    for (int i = 0; i < n; i++) {
      cout << s[i] << endl;
    }
  }
}
