#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 2e5 + 5;

int n, m;
int a[N] = {0}, b[N] = {0};

bool chk(int k) {
	long long ans = 0ll;
	for (int i = 1; i <= m; i++)
		ans += max(0, a[i] - k);
	return ans <= 1ll * k * (n - k); 
}

void slv() {
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= m; i++)
		scanf("%d", &a[i]);
	int l = -1, r = min(n, m);
	while (l + 1 < r) {
		int mid = (l + r) / 2;
		if (chk(mid))
			r = mid;
		else
			l = mid;
	} 
	for (int i = 1; i <= m; i++) 
		b[i] = max(0, a[i] - r);
	vector<vector<char> > ans(n + 1, vector<char>(m + 1, '.'));
	for (int i = 1; i <= r; i++) {
		int pos = n - r + i;
		for (int j = 1; j <= m; j++) {
			while (b[j] > 0 && pos > 1)
				ans[pos][j] = '#', b[j]--, pos--;
			ans[pos][j] = '#';
		}
	}
	for (int j = 1; j <= m; j++) {
		int tot = 0;
		for (int i = 1; i <= n; i++)
			if (tot == a[j])
				ans[i][j] = '.';
			else if (ans[i][j] == '#')
				tot++;
	}
	cout << r << endl;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++)
			cout << ans[i][j];
		cout << endl;
	}
}

int main() {
	int T;
	scanf("%d", &T);
	while (T--)
		slv();	
	return 0;
}