#include<iostream>

#include<vector>

using namespace std; 

char map[1000][1000]; //map[row][column]  

int dir[4][2]={{0,1},{-1,0},{0,-1},{1,0}};

struct Point
{
	int x;
	int y;
};
short dist[1000][1000];

vector<Point> vec;

Point temppoint;

int startx,starty;

int max_dist;
   
void search(int i,int j,int distance)  
{  
	int k;
	for(k=0;k<4;k++)
	{
		if(map[i+dir[k][0]][j+dir[k][1]]=='.')
		{
			map[i+dir[k][0]][j+dir[k][1]]='1';

			temppoint.x=i+dir[k][0];

			temppoint.y=j+dir[k][1];

			vec.push_back(temppoint);

			dist[i+dir[k][0]][j+dir[k][1]]=distance+1;

			max_dist=distance+1;

			startx=i+dir[k][0];

			starty=j+dir[k][1];
		}
	}
}

   
int main()  
{  
	int n,x,y,j,k,l;  
	cin>>n;  
	while(n--)
	{
		memset(dist,0,sizeof(dist));
		memset(map,'\0',sizeof(map));
		startx=starty=0;
		max_dist=0;
		cin>>x>>y; //y row x column
		for(j=0;j<y;j++) 
			cin>>map[j];    
		k=l=0;  
		while(map[k][l]=='#') //找到第一个'.',一列一列的找 
		{  
			if(k<y-1) k++;  
			else 
			{
				k=0;
				l++;
			}  
		}
		map[k][l]='1';
		temppoint.x=k;
		temppoint.y=l;
		vec.clear();
		vec.push_back(temppoint);

		int qh=0;
		while(qh<vec.size())
		{
			search(vec[qh].x,vec[qh].y,dist[vec[qh].x][vec[qh].y]);
			qh++;
		}
		for(k=0;k<y;k++)
		{
			for(l=0;l<x;l++)
			{
				if(map[k][l]=='1')
					map[k][l]='.';
			}
		}
		memset(dist,0,sizeof(dist));
		
		vec.clear();

		temppoint.x=startx;

		temppoint.y=starty;

		map[startx][starty]='1';

		vec.push_back(temppoint);

		max_dist=0;

		qh=0;

		while(qh<vec.size())
		{
			search(vec[qh].x,vec[qh].y,dist[vec[qh].x][vec[qh].y]);
			qh++;
		}
		cout<<"Maximum rope length is "<<max_dist<<"."<<endl;
			
	}  
	return 0;  
}