#include <bits/stdc++.h>
using namespace std;
int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int t;
  cin >> t;
  for (int i = 0; i < t; i++){
    int n, m;
    cin >> n >> m;
    vector<int> a(m);
    for (int j = 0; j < m; j++){
      cin >> a[j];
    }
    int tv = n, fv = 0;
    while (tv - fv > 1){
      int mid = (tv + fv) / 2;
      long long sum = 0;
      for (int j = 0; j < m; j++){
        sum += max(a[j] - mid, 0);
      }
      if (sum <= (long long) mid * (n - mid)){
        tv = mid;
      } else {
        fv = mid;
      }
    }
    int P = tv;
    vector<vector<int>> cnt(P, vector<int>(m, 1));
    int r = 0, s = 0;
    for (int j = 0; j < m; j++){
      for (int k = 0; k < max(a[j] - P, 0); k++){
        if (s == n - P){
          r++;
          s = 0;
        }
        cnt[r][j]++;
        s++;
      }
    }
    for (int j = 0; j < m; j++){
      int s = 0;
      for (int k = 0; k < P; k++){
        cnt[k][j] = min(cnt[k][j], a[j] - s);
        s += cnt[k][j];
      }
    }
    vector<int> p(m, 0);
    vector<vector<char>> c(n, vector<char>(m, '.'));
    for (int j = 0; j < P; j++){
      for (int k = m - 1; k >= 0; k--){
        if (k < m - 1){
          p[k] = max(p[k], p[k + 1] - 1);
        }
        for (int l = 0; l < cnt[j][k]; l++){
          c[p[k]][k] = '#';
          p[k]++;
        }
      }
    }
    cout << P << endl;
    for (int j = 0; j < n; j++){
      for (int k = 0; k < m; k++){
        cout << c[j][k];
      }
      cout << '\n';
    }
  }
}