#include <bits/stdc++.h>

void solve(){
    int n, m;
    std::cin >> n >> m;
    std::vector<int> a(m);
    for(int i = 0; i < m; i++){
        std::cin >> a[i];
    }

    auto construct = [&](int k) {
        std::vector res(n, std::vector<int>(m));
        std::vector<int> b;
        for (int i = 0; i < std::max(a[0], k); i += 1) {
            b.emplace_back(i);
            res[i][0] = 1;
        }
        for (int j = 1; j < m; j += 1) {
            int x = std::max(k, a[j]);
            
            for (int i = int(b.size()) - 1; i >= 0 && x; i -= 1) {
                int y = b[i];
                res[y][j] = 1;
                y += 1;
                x -= 1;
            }
            std::vector<int> new_b;
            b.emplace_back(n);
            for (int i = int(b.size()) - 2; i >= 0; i -= 1) {
                int y = b[i] + 1;
                while(x && y < b[i + 1]) {
                    res[y][j] = 1;
                    y += 1;
                    x -= 1;
                }
                new_b.emplace_back(y - 1);
            }
            std::reverse(new_b.begin(), new_b.end());
            b = new_b;


        }
        for (int j = 0; j < m; j += 1) {
            int cnt = 0;
            for (int i = 0; i < n; i += 1) {
                cnt += res[i][j];
            }
            for (int i = n - 1; i >= 0 && cnt > a[j]; i -= 1) {
                if (res[i][j]) {
                    res[i][j] = 0;
                    cnt -= 1;
                }
            }
        }
        for (int i = n - 1; i >= 0; i -= 1) {
            for (int j = 0; j < m; j += 1) {
                std::cout << ".#"[res[i][j]];
            }
            std::cout << "\n";
        }
    };

    for (int k = 0; k <= n; k += 1) {
        int sum = 0;
        for (int i = 0; i < m; i += 1) {
            sum += std::max(0, a[i] - k);
        }
        if (sum <= 1ll * k * (n - k)) {
            std::cout << k << "\n";
            construct(k);
            return;
        }
    }
} 

int main(){
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(0);
    std::cout.tie(0);
    int T;
    std::cin >> T;
    while(T--){
        solve();
    }

    return 0;
}