#include <map>
#include <set>
#include <array>
#include <cmath>
#include <deque>
#include <bitset>
#include <random>
#include <string>
#include <vector>
#include <cassert>
#include <complex>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>

using namespace std;

const int MAXN = 2e5 + 100;
int a[MAXN];
string out[MAXN];

int n, m;

bool check(int k) {
    vector<int> h(k, 0);
    for (int i = m - 1; i >= 0; --i) {
        for (int j = 0; j < n; ++j) {
            out[j][i] = '.';
        }
        int c = a[i];
        for (int j = 0; j < k && c > 0; ++j) {
            if (h[j] > 0) {
                --c;
                out[h[j] - 1][i] = '#';
            }
        }
        for (int j = k - 1; j >= 0; --j) {
            int can_go;
            if (j != 0) {
                can_go = h[j - 1] - h[j] - 1;
            } else {
                can_go = n - h[j];
            }
            if (can_go <= 0) continue;
            can_go = min(can_go, c);
            c -= can_go;
            for (int t = 0; t < can_go; ++t) {
                ++h[j];
                out[h[j] - 1][i] = '#';
            }
        }
        if (c > 0) return false;
    }
    return true;
}

void solve() {
    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        cin >> a[i];
    }
    for (int i = 0; i < n; ++i) {
        out[i].clear();
        out[i].resize(m, '.');
    }
    
    int l = -1, r = n + 1;
    while (r - l > 1) {
        int m = (l + r) / 2;
        if (check(m)) {
            r = m;
        } else {
            l = m;
        }
    }
    cout << r << "\n";
    check(r);
    for (int i = 0; i < n; ++i) {
        cout << out[i] << "\n";
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int tst;
    cin >> tst;
    while (tst--) solve();
    
    return 0;
}