#include <bits/stdc++.h>

using namespace std;

void solve() {
    int n, m;
    cin >> n >> m;
    vector<int> a(m);
    for (auto &i: a)cin >> i;
    int lres = -1, rres = n * m + 2;
    while (rres - lres > 1) {
        int mid = (rres + lres) / 2;
        bool ok{true};
        vector<int> dp(n, 0);
        for (int i = 0; i < m; ++i) {
            int l = -1, r = n - a[i] + 1;
            while (r - l > 1) {
                int mm = (r + l) / 2;
                int cur = (mm ? dp[mm - 1] : 0);
                int mx = cur;
                for (int j = 0; j < a[i]; ++j) {
                    mx = max(mx, cur + 1);
                    if (j + 1 < a[i])cur = max(cur, dp[mm + j]);
                }
                if (mx <= mid) {
                    l = mm;
                } else r = mm;
            }
            if (~l) {
                for (int j = a[i] - 1; ~j; --j) {
                    dp[l + j] = max(dp[l + j], (l + j - 1 >= 0 ? dp[l + j - 1] : 0) + 1);
                }
                for (int j = 1; j < n; ++j)dp[j] = max(dp[j], dp[j - 1]);
            } else {
                ok = false;
                break;
            }
        }
        if (ok) {
            rres = mid;
        } else lres = mid;
    }
//    cout << rres << "\n";
    vector<int> dp(n, 0);
    vector<vector<char>> res(n, vector<char>(m, '.'));
    for (int i = 0; i < m; ++i) {
        int l = -1, r = n - a[i] + 1;
        while (r - l > 1) {
            int mm = (r + l) / 2;
            int cur = (mm ? dp[mm - 1] : dp[mm]);
            int mx = cur;
            for (int j = 0; j < a[i]; ++j) {
                mx = max(mx, cur + 1);
                if (j + 1 < a[i])cur = max(cur, dp[mm + j]);
            }
            if (mx <= rres) {
                l = mm;
            } else r = mm;
        }
        assert(~l);
        for (int j = a[i] - 1; ~j; --j) {
            dp[l + j] = max(dp[l + j], (l + j - 1 >= 0 ? dp[l + j - 1] : 0) + 1);
            res[l + j][i] = '#';
        }
        for (int j = 1; j < n; ++j)dp[j] = max(dp[j], dp[j - 1]);
    }
    cout << rres << "\n";
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            cout << res[i][j];
        }
        cout << "\n";
    }

}

int main() {
    cin.tie(0)->sync_with_stdio(false);
    int t;
    cin >> t;
    while (t--)solve();
}