// Problem:  LIS on Grid
// Contest: Virtual Judge - QOJ
// URL: https://vjudge.csgrandeur.cn/problem/QOJ-7943
// Memory Limit: 253 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
using namespace std;
const long long inf = 1e18;
const int mininf = 1e9 + 7;
#define int long long
#define pb emplace_back
inline int read(){int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}return x*f;}
inline void write(int x){if(x<0){x=~(x-1);putchar('-');}if(x>9)write(x/10);putchar(x%10+'0');}
#define put() putchar(' ')
#define endl puts("")
const int MAX = 3e5 + 10;
int a[MAX];
map <int, int> mp[MAX];
int b[MAX];

void solve(){
	int n = read(), m = read();
	for(int i = 1; i <= m; i++){
		a[i] = read();
	}
	int l = 0, r = m;
	while(l <= r){
		int mid = (l + r) >> 1;	
		int cnt = 0;
		for(int i = 1; i <= m; i++){
			b[i] = a[i] - mid;
			b[i] = max(0ll, b[i]);
			cnt += b[i];
		}
		if(cnt > (n - mid) * mid){
			l = mid + 1;
		}else{
			r = mid - 1;
		}
	}
	write(l), endl;
	int k = l;
	for(int i = 1; i <= m; i++){
		b[i] = a[i] - k;
		b[i] = max(0ll, b[i]);
	}
	for(int i = n - k + 1; i <= n; i++){
		int now = 1;
		int nowy = i;
		int cnt = n - k;
		while(now <= m){
			mp[nowy][now] = 1;
			while(b[now] and cnt){
				cnt--, b[now]--;
				nowy--;
				mp[nowy][now] = 1;
			}
			now++;
		}
		now = m;
		while(nowy > (i - (n - k + 1) + 1)){
			nowy--;
			mp[nowy][now] = 1;
		}
	}
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= m; j++){
			if(mp[i][j] and a[j])	putchar('#'), a[j]--;
			else putchar('.');
		}endl;
	}
	for(int i = 1; i <= n; i++){
		mp[i].clear();
	}
}

signed main(){
	int t = read();
	while(t--)	solve();
	return 0;
}