#include <bits/stdc++.h>
#define rep(i,n) for(int i=0,del##i##verme=int(n);i<del##i##verme;++i)
#define rep1(i,n) for(int i=1,parano##i##a=int(n);i<=parano##i##a;++i)
#define per(i,n) for(int i=int(n)-1;i>=0;--i)
#define per1(i,n) for(int i=int(n);i>=1;--i)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define y0 LingLuo
#define y1 VividCycle
typedef long long ll;
typedef unsigned long long ull;
typedef long double ldb;
using namespace std;
const ll mod1=998244353;
const ll mod2=1000000007;
unsigned time_related_rand()
{
	return unsigned(std::chrono::steady_clock::now().time_since_epoch().count());
}
int t,n,m;
int a[200005];
string s[200005];
bool check(int k)
{
	int ss=0;
	rep1(i,m) ss+=max(0,a[i]-k);
	return ss<=k*(n-k); 
}
vector<int> qt;
void Q()
{
	cin>>n>>m;
	rep1(i,m)
	{
		cin>>a[i];
	}
	int l=-1,r=n,tm;
	while(r-l>1)
	{
		tm=(l+r)>>1;
		if(check(tm)) r=tm;
		else l=tm;
	}
	++l;
	qt.clear();
	rep1(i,l) qt.pb(i);
	rep1(i,n)
	{
		s[i]="";
		rep(j,m) s[i]+='.';
	}
	rep1(i,m)
	{
		if(a[i]<=l)
		{
			rep(j,a[i]) s[qt[j]][i-1]='#';
		}
		else
		{
			a[i]-=l;
			for(int x:qt) s[x][i-1]='#';
			per(j,qt.size())
			{
				while(a[i]&&qt[i]<n&&s[qt[j]+1][i-1]=='.') s[++qt[j]][i-1]='#',--a[i];
				if(!a[i])break;
			}
		}
	}
	cout<<l<<'\n';
	per1(i,n) cout<<s[i]<<'\n';
}
int main()
{
	ios_base::sync_with_stdio(false);cin.tie(0);
	cin>>t;while(t--)Q();return 0;
}
/* things to check
1.  int overflow or long long memory need
2.  recursion/array/binary search/dp/loop bounds
3.  precision
4.  special cases(n=1,bounds)
5.  delete debug statements
6.  initialize(especially multi-tests)
7.  = or == , n or m ,++ or -- , i or j , > or >= , < or <=
8.  keep it simple and stupid
9.  do not delete, use // instead
10. operator priority
11. is there anything extra to output?
12. ...
*/

/* something to think about
1. greedy? dp? searching? dp with matrix/ segment tree? binary search?
2. If contains "not", why not ?????? or few affect?
*/