#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>

using namespace std;

const int M = 1015;

int i,j,k;

int Max (int x ,int y)
{
return x>y?x:y ;
}

struct p
{
    int x;
    int y;
    int step;
};

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

char a[M][M];
int visit[M][M];
int n,m;
int tmpx,tmpy;
int tmp;

void bfs(int x,int y)
{
    memset(visit,0,sizeof(visit));
    int i;
    p t;
    p s;
    t.x = x;
    t.y = y;
    t.step = 0;
    queue<p>q;

    q.push(t);
    visit[t.x][t.y] = 1;
    while(!q.empty()){
        p w;
        w = q.front();
        q.pop();
        for(i=0;i<4;i++){
            s.x = w.x + dir[i][0];
            s.y = w.y + dir[i][1];

            if(s.x>=0&&s.x<n&&s.y>=0&&s.y<m&&visit[s.x][s.y]==0&&a[s.x][s.y]!='#'){
                s.step = w.step + 1;
                visit[s.x][s.y] = 1;
                if(s.step > tmp){
                tmpx = s.x;
                tmpy = s.y;
                tmp = s.step;
            }
                q.push(s);
            }
        }
    }

}

int main ()
{
    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        memset(a,0,sizeof(a));
        int i;
        for(i=0;i<m;i++){
            scanf("%s",a[i]);
        }
        int x,y;
        for(i=0;i<m;i++){
                int f = 0;
                for(j=0;j<n;j++){
                    if(a[i][j] == '.') {
                        x = i;
                        y = j;
                        f = 1;
                        break ;
                    }
                }
                if(f) break;
        }
        bfs(x,y);
        x = tmpx;
        y = tmpy;
        bfs(x,y);
        int  ans = tmp;
        printf("Maximum rope length is %d.\n",ans);

    }


return 0;
}