#include <bits/stdc++.h>

using i64 = long long;

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];
    }
    
    std::vector<std::string> ans;

    auto check = [&](int k) {
        std::vector<int> f(k);
        for (int i = 0; i < k; i++) {
            f[i] = n - k + i;
        }
        ans.assign(n, std::string(m, '.'));
        for (int j = 0; j < m; j++) {
            int res = a[j];
            for (int i = k - 1; i >= 0; i--) {
                if (res > 0) {
                    ans[f[i]][j] = '#';
                    res--;
                }
            }
            for (int i = k - 1; i >= 0; i--) {
                while (res > 0 && f[i] > (i ? f[i - 1] + 1 : 0)) {
                    res--;
                    f[i]--;
                    ans[f[i]][j] = '#';
                }
            }
            if (res > 0) {
                return false;
            }
        }
        return true;
    };

    int lo = 1, hi = n;
    while (lo < hi) {
        int m = (lo + hi) / 2;
        if (check(m)) {
            hi = m;
        } else {
            lo = m + 1;
        }
    }
    std::cout << lo << "\n";
    check(lo);
    for (int i = 0; i < n; i++) {
        std::cout << ans[i] << "\n";
    }
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int t;
    std::cin >> t;

    while (t--) {
        solve();
    }

    return 0;
}