#include <bits/stdc++.h>
#define long long long int
#define DEBUG
using namespace std;

// @author: pashka

struct test {
    int n, m;
    vector<int> a;

    vector<string> ans;

    bool can(int x) {
        ans.assign(n, string(m, '.'));
        vector<int> d(n + 1);
        for (int i = 0; i < m; i++) {
            int k = a[i];
            for (int j = 0; j < n; j++) {
                if (d[j] < d[j + 1] && k > 0) {
                    ans[j][i] = '#';
                    k--;
                }
            }
            if (k > 0 && d[n] == d[n - 1] && d[n] < x) {
                ans[n - 1][i] = '#';
                k--;
            }
            for (int j = n - 1; j >= 0; j--) {
                if (ans[j][i] == '.' && k > 0 && d[j] < x - 1) {
                    ans[j][i] = '#';
                    k--;
                }
            }
            for (int j = n - 1; j >= 0; j--) {
                if (ans[j][i] == '.' && k > 0 && d[j] < x) {
                    ans[j][i] = '#';
                    k--;
                }
            }
            if (k > 0) return false;
            for (int j = n; j > 0; j--) {
                if (ans[j - 1][i] == '#') {
                    d[j] = max(d[j], d[j - 1] + 1);
                }
            }
        }
        return true;
    }

    void solve() {
        cin >> n >> m;
        a.resize(m);
        for (int i = 0; i < m; i++) {
            cin >> a[i];
        }
        // can(2);
        int l = 0;
        int r = n;
        while (r > l + 1) {
            int x = (l + r) / 2;
            if (can(x)) {
                r = x;
            } else {
                l = x;
            }
        }
        can(r);
        int res = r;
        cout << res << "\n";
        for (string& s: ans) cout << s << "\n";
    }
};

int main() {
    ios::sync_with_stdio(false);

    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        test().solve();
    }

    return 0;
}