#include <bits/stdc++.h>
using i64 = long long;
using namespace std;
const int N = 1e3 + 5;
// const int B = 205;
// const int M = 2e4 + 5;
// const int base = 13331;
// const int mod = 998244353;
// const int mod = 1e9 + 7;
// const double pi = acos(-1);

void solve(int _num)
{
    int n, m;
    cin >> n >> m;
    vector<int> a(m + 1);
    for (int i = 1; i <= m; i++)
        cin >> a[i];
    auto b = a;
    auto check = [&](int k) -> bool
    {
        int res = 0;
        for (int i = 1; i <= n; i++)
            res += max(0, a[i] - k);
        return res <= k * (n - k);
    };
    int l = 0, r = min(n, m), mid;
    while (l < r)
    {
        mid = l + r >> 1;
        if (check(mid))
            r = mid;
        else
            l = mid + 1;
    }
    cout << r << '\n';
    vector<vector<int>> ans(n + 1, vector<int>(m + 1));
    for (int i = n - r + 1; i <= n; ++i)
    {
        int x = i;
        for (int j = 1; j <= m; ++j)
        {
            ans[x][j] = 1;
            while (x > i - n + r && a[j] > r)
            {
                --a[j];
                ans[--x][j] = 1;
            }
        }
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
            if (b[j] && ans[i][j])
                cout << '#', b[j]--;
            else
                cout << '.';
        cout << '\n';
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    cin >> t;
    cout << fixed << setprecision(18);
    for (int i = 1; i <= t; i++)
        solve(i);
}