#include <bits/stdc++.h>
using namespace std;
const long long int mod = (long long int)(998244353);
long long int test = 1;
vector<long long int> read(int n) {
  vector<long long int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  return v;
}
void solve() {
  long long int i, j, k, m, n, cnt = 0, ans = 0, sum = 0;
  cin >> n;
  std::vector<string> v(n);
  for (auto &it : v) {
    cin >> it;
  }
  unordered_map<string, long long int> mp;
  for (auto it : v) {
    mp[it]++;
  }
  for (auto &it : v) {
    if (mp[it] > 1) {
      bool ok = 0;
      for (long long int i = 0; i <= 3; i++) {
        string first = it.substr(0, i);
        for (long long int j = 0; j <= 9; j++) {
          string temp;
          if (i + 1 < n) {
            temp = it.substr(i + 1, 3 - i);
          }
          string res = first + (char)('0' + j) + temp;
          if (mp.find(res) == mp.end() || mp[res] == 0) {
            mp[it]--;
            mp[res]++;
            it = res;
            ok = 1;
            ans++;
            break;
          }
        }
        if (ok) break;
      }
    }
  }
  cout << ans << "\n";
  for (auto it : v) {
    cout << it << "\n";
  }
  test++;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int i = 1;
  int t;
  cin >> t;
  while (t--) solve();
  return 0;
}
