#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
vector<string> v, an;
map<string, int> m, m1;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
      string s;
      cin >> s;
      m[s]++;
      m1[s]++;
      v.push_back(s);
    }
    int ans = 0;
    for (int i = 0; i < n; i++) {
      string s = v[i];
      ans += max(0, m[s] - 1);
      m[s] = 0;
      if (m1[s] == 1) {
        an.push_back(s);
        continue;
      }
      bool tt = false;
      for (int z = 0; z < 4; z++) {
        for (int k = 0; k <= 9; k++) {
          string ss = s;
          ss[z] = '0' + k;
          if (m1[ss] == 0) {
            an.push_back(ss);
            m1[ss]++;
            m1[s]--;
            tt = true;
          }
          if (tt) break;
        }
        if (tt) break;
      }
    }
    cout << ans << endl;
    for (int i = 0; i < n; i++) cout << an[i] << endl;
    m.clear();
    m1.clear();
    an.clear();
    v.clear();
  }
}
