#include<bits/stdc++.h>
using namespace std;
int n,m,a[300005];
int f[300005],pn[300005];
char mp[300005];
bool check(int k){
	for(int j=1;j<=n;j++) f[j]=0;
	for(int i=1;i<=m;i++){
		int pos=-1;
		for(int j=n;j>=1;j--){
			int val=f[(i-1)*n+j];
			if(pos!=-1&&pos-a[i]>=j){
				f[i*n+j]=val;
				continue;
			}
			if(j>1) val=max(val,f[(i-1)*n+j-1]+1);
			else val=max(val,1);
			if(pos==-1&&val<=k){
				if(j<a[i]) return 0;
				pos=pn[i]=j;
			}
			if(pos!=-1){
				f[i*n+j]=val;
				continue;
			}
			else f[i*n+j]=f[(i-1)*n+j];
		}
		if(pos==-1) return 0;
	}
	return 1;
}
void solve(){
	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<=r){
		int mid=(l+r)/2;
		if(check(mid)) r=mid-1;
		else l=mid+1;
	}
	check(l);
	printf("%d\n",l);
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(pn[j]-a[j]<i&&i<=pn[j]) putchar('#');
			else putchar('.');
		}
		puts("");
	}
}
int main(){
	int t;
	scanf("%d",&t);
	while(t--) solve();
}