#include <bits/stdc++.h>

using namespace std;

#define DIM 200007

int n, m, a[DIM], pos[DIM], mn[DIM];

set<pair<int, int> > s;

bool cando(int k){
    s.clear();
    for(int i = 1; i <= k; ++i) {pos[i] = n; mn[i] = n - a[i] + 1; s.insert({i - mn[i], -i});}
    int currmax = n;
    for(int i = k + 1; i <= m; ++i){
        pos[i] = min(k - (*s.begin()).first, currmax);
        //if(k == 2) cout << i << ' ' << pos[i] << endl;
        if(pos[i] - a[i] + 1 < 1) return false;
        mn[i] = pos[i] - a[i] + 1;
        currmax = pos[i];
        pair<int, int> p = *s.begin();
        //cout << p.first << ' ' << p.second << endl;
        s.erase(p);
        vector<pair<int, int> > need_to_del;
        for(auto P : s){
            int id = -P.second;
            if(id > -p.second) need_to_del.push_back(P);
        }
        for(auto P : need_to_del){
            s.erase(P);
            s.insert({P.first - 1, P.second});
        }
        s.insert({k - mn[i], -i});
    }
    return true;
}

void solve(){
    cin >> n >> m;
    for(int i = 1; i <= m; ++i) cin >> a[i];
    int l = 1;
    int r = min(n, m);
    while(l < r){
        int m = (l + r) >> 1;
        if(cando(m)) r = m;
        else l = m + 1;
    }
    cout << l << endl;
    cando(l);
    for(int i = 1; i <= n; ++i){
        for(int j = 1; j <= m; ++j){
            if(i < mn[j] || i > pos[j]) cout << '.';
            else cout << '#';
        }
        cout << endl;
    }
    return;
}

int main()
{
    int t = 0;
    cin >> t;
    while(t--){
        solve();
    }
    return 0;
}