#include <bits/stdc++.h>
using namespace std;
vector<string> gans;
inline bool Check(int n, int m, vector<int> num, int lim) {
    vector<int> sp;
    vector<string> ans(n, string(m, '.'));
    for (int i = 0; i < m; ++i) {
        if (num[i] <= sp.size()) {
            for (int j = 0; j < num[i]; ++j) ans[sp[j]][i] = '#';
        } else {
            for (auto x : sp) ans[x][i] = '#';
            int rm = num[i] - sp.size();
            for (int j = 0; j < sp.size(); ++j) {
                int &x = sp[j];
                while (rm && x > n - lim + j) {
                    if (x == 0 || ans[x - 1][i] == '#') break;
                    --x; --rm;
                    ans[x][i] = '#';
                }
            }
            if (rm && sp.size() < lim) {
                sp.push_back(n);
                int j = sp.size() - 1;
                int &x = sp[j];
                while (rm && x > n - lim + j) {
                    if (x == 0 || ans[x - 1][i] == '#') break;
                    --x; --rm;
                    ans[x][i] = '#';
                }
            }
            for (int j = 0; j < sp.size(); ++j) {
                int &x = sp[j];
                while (rm) {
                    if (x == 0 || ans[x - 1][i] == '#') break;
                    --x; --rm;
                    ans[x][i] = '#';
                }
            }
            if (rm) return 0;
        }
    }
    gans = ans;
    return 1;
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int Case;
    cin >> Case;
    while (Case--) {
        int n, m;
        cin >> n >> m;
        vector<int> num(m);
        for (int i = 0; i < m; ++i) cin >> num[i];
        int ans = -1;
        gans.clear();
        for (int l = 0, r = n; l <= r; ) {
            int mid = (l + r) >> 1;
            if (Check(n, m, num, mid)) ans = mid, r = mid - 1; else l = mid + 1;
        }
        cout << ans << '\n';
        for (const auto &s : gans) cout << s << '\n';
    }
    return 0;
}