#include <bits/stdc++.h>
#define pb emplace_back
#define fst first
#define scd second
#define mkp make_pair
#define mems(a, x) memset((a), (x), sizeof(a))

using namespace std;
typedef long long ll;
typedef double db;
typedef unsigned long long ull;
typedef long double ldb;
typedef pair<ll, ll> pii;

const int maxn = 200100;

int n, m, a[maxn], b[maxn];

inline bool check(int x) {
	int s = 0;
	for (int i = 1; i <= m; ++i) {
		s += max(0, a[i] - x);
	}
	return s <= x * (n - x);
}

void solve() {
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= m; ++i) {
		scanf("%d", &a[i]);
		b[i] = a[i];
	}
	int l = 0, r = min(n, m), k = -1;
	while (l <= r) {
		int mid = (l + r) >> 1;
		if (check(mid)) {
			k = mid;
			r = mid - 1;
		} else {
			l = mid + 1;
		}
	}
	printf("%d\n", k);
	vector< vector<int> > ans(n + 2, vector<int>(m + 2, 0));
	for (int i = n - k + 1; i <= n; ++i) {
		int x = i;
		for (int j = 1; j <= m; ++j) {
			ans[x][j] = 1;
			while (x > 1 && a[j] > k) {
				--a[j];
				ans[--x][j] = 1;
			}
		}
	}
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= m; ++j) {
			if (b[j] && ans[i][j]) {
				putchar('#');
				--b[j];
			} else {
				putchar('.');
			}
		}
		putchar('\n');
	}
}

int main() {
	int T = 1;
	scanf("%d", &T);
	while (T--) {
		solve();
	}
	return 0;
}