#include<cstdio>
#include<queue>
#include<algorithm>
#include<vector>
#include<cstring>
using namespace std;int T,n,m;
char s[50][50];
int Belong[50][50],block,use[50*50];
int dx[]={0,0,-1,1};
int dy[]={1,-1,0,0};int h[50*50];
struct Edge
{int from,to,nx;
}e[100000];
int sz;bool ok(int x,int y)
{if(x>=0&&x<n&&y>=0&&y<m) return 1;return 0;
}void dfs(int x,int y)
{Belong[x][y]=block;if(ok(x-1,y)&&s[x][y]==s[x-1][y]&&Belong[x-1][y]==0) dfs(x-1,y);if(ok(x+1,y)&&s[x][y]==s[x+1][y]&&Belong[x+1][y]==0) dfs(x+1,y);if(ok(x,y-1)&&s[x][y]==s[x][y-1]&&Belong[x][y-1]==0) dfs(x,y-1);if(ok(x,y+1)&&s[x][y]==s[x][y+1]&&Belong[x][y+1]==0) dfs(x,y+1);
}void add(int x,int y)
{e[sz].from=x; e[sz].to=y; e[sz].nx = h[x];h[x]=sz++;
}int main()
{scanf("%d",&T);while(T--){scanf("%d%d",&n,&m);for(int i=0;i<n;i++) scanf("%s",s[i]);memset(Belong,block=0,sizeof Belong);sz=0;memset(h,0xff,sizeof(h));for(int i=0;i<n;i++){for(int j=0;j<m;j++){if(Belong[i][j]) continue;block++; dfs(i,j);}}for(int i=0;i<n;i++){for(int j=0;j<m;j++){for(int k=0;k<4;k++){int x=i+dx[k];int y=j+dy[k];if(!ok(x,y)) continue;if(Belong[i][j]==Belong[x][y]) continue;add(Belong[i][j],Belong[x][y]);}}}int ans=0x7fffffff;for(int i=1;i<=block;i++){memset(use,-1,sizeof(use));int mx=0;use[i]=0;queue<int>q;q.push(i);while(!q.empty()){int x=q.front();q.pop();for(int j=h[x];j!=-1;j=e[j].nx){int y=e[j].to;if(use[y]!=-1) continue;use[y]=use[x]+1;mx=max(use[y],mx);q.push(y);}}ans=min(mx,ans);}printf("%d\n",ans);}return 0;
}