#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 5;
string s[maxn];
pair<string, int> p[maxn];
int n;
void change(int index) {
  for (int i = 0; i < 4; i++) {
    char temp = s[index][i];
    for (int j = '0'; j <= '9'; j++) {
      s[index][i] = j;
      int flag = 1;
      for (int k = 1; k <= n; k++) {
        if (k == index) continue;
        if (s[index] == s[k]) {
          flag = 0;
          break;
        }
      }
      if (flag) return;
    }
    s[index][i] = temp;
  }
}
int cmp(pair<string, int> x, pair<string, int> y) {
  return x.second < y.second;
}
int main() {
  ios::sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--) {
    cin >> n;
    for (int i = 1; i <= n; i++) {
      cin >> s[i];
      p[i].first = s[i];
      p[i].second = i;
    }
    sort(p + 1, p + n + 1);
    for (int i = 1; i <= n; i++) s[i] = p[i].first;
    int ans = 0;
    for (int i = 1; i <= n - 1; i++) {
      if (s[i] == s[i + 1]) {
        change(i);
        ans++;
      }
    }
    for (int i = 1; i <= n; i++) p[i].first = s[i];
    sort(p + 1, p + n + 1, cmp);
    for (int i = 1; i <= n; i++) s[i] = p[i].first;
    cout << ans << endl;
    for (int i = 1; i <= n; i++) {
      cout << s[i] << endl;
    }
  }
}
