#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <cctype>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <list>
#include <cmath>
#include <bitset>
#define rap(i, a, n) for(int i=a; i<=n; i++)
#define rep(i, a, n) for(int i=a; i<n; i++)
#define lap(i, a, n) for(int i=n; i>=a; i--)
#define lep(i, a, n) for(int i=n; i>a; i--)
#define rd(a) scanf("%d", &a)
#define rlld(a) scanf("%lld", &a)
#define rc(a) scanf("%c", &a)
#define rs(a) scanf("%s", a)
#define rb(a) scanf("%lf", &a)
#define rf(a) scanf("%f", &a)
#define pd(a) printf("%d\n", a)
#define plld(a) printf("%lld\n", a)
#define pc(a) printf("%c\n", a)
#define ps(a) printf("%s\n", a)
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 110000, INF = 0x7fffffff;int n, m;
string str[15];
int dis[4][2] = {{1, 0},{-1, 0},{0, 1},{0, -1}};
int vis[15][15], vis1[15][15], d[15][15];void dfs(int x, int y, int cnt)
{for(int i = 0; i < 4; i++){int nx = x + dis[i][0];int ny = y + dis[i][1];if(nx < 0 || nx >= n || ny < 0 || ny >=m || str[nx][ny] == '.' || vis[nx][ny]) continue;vis[nx][ny] = cnt;dfs(nx, ny, cnt);}
}struct node
{int x, y;node(int x, int y) : x(x), y(y) {}
};int spfa(int x, int y)
{for(int i = 0; i <= n; i++)for(int j = 0; j <= m; j++) d[i][j] = INF;vector<node> f;mem(vis1, 0);queue<node> Q;Q.push(node(x, y));vis1[x][y] = 1;d[x][y] = 0;while(!Q.empty()){node u = Q.front(); Q.pop();f.push_back(u);vis1[u.x][u.y] = 0;for(int i = 0; i < 4; i++){node t = node(0, 0);t.x = u.x + dis[i][0];t.y = u.y + dis[i][1];if(t.x < 0 || t.x >= n || t.y < 0 || t.y >= m || str[t.x][t.y] == '.') continue;if(d[t.x][t.y] > d[u.x][u.y] + 1){d[t.x][t.y] = d[u.x][u.y] + 1;if(!vis1[t.x][t.y]){vis1[t.x][t.y] = 1;Q.push(t);}}}}int mx = -INF;for(int i = 0; i < f.size(); i++){mx = max(mx, d[f[i].x][f[i].y]);}return mx;
}set<int> s1, s2;vector<node> G;int bfs(int x1, int y1, int x2, int y2)
{queue<node> Q;for(int i = 0; i <= n; i++)for(int j = 0; j <= m; j++) d[i][j] = INF;vector<node> f;d[x1][y1] = d[x2][y2] = 0;Q.push(node(x1, y1)); Q.push(node(x2, y2));mem(vis1, 0);vis1[x1][y1] = 1, vis1[x2][y2] = 1;while(!Q.empty()){node u = Q.front(); Q.pop();f.push_back(u);vis1[u.x][u.y] = 0;for(int i = 0; i < 4; i++){node t = node(0, 0);t.x = u.x + dis[i][0];t.y = u.y + dis[i][1];if(t.x < 0 || t.x >= n || t.y < 0 || t.y >= m || str[t.x][t.y] == '.') continue;if(d[t.x][t.y] > d[u.x][u.y] + 1){d[t.x][t.y] = d[u.x][u.y] + 1;if(!vis1[t.x][t.y]){vis1[t.x][t.y] = 1;Q.push(t);}}}}int mx = -INF;for(int i = 0; i < f.size(); i++){mx = max(mx, d[f[i].x][f[i].y]);}return mx;}int main()
{int T, kase = 0;rd(T);while(T--){s1.clear();s2.clear();mem(vis, 0);int cnt = 0;G.clear();rd(n), rd(m);for(int i = 0; i < n; i++){cin >> str[i];for(int j = 0; j < m; j++)if(str[i][j] == '#') G.push_back(node(i, j));}//  cout << 11111 <<endl;for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)if(!vis[i][j] && str[i][j] == '#'){cnt++;vis[i][j] = cnt;dfs(i, j, cnt);}//cout << cnt << endl;printf("Case %d: ", ++kase);if(cnt > 2){printf("-1\n");continue;}if(cnt == 0){printf("0\n");continue;}if(cnt == 1){for(int i = 0; i < G.size(); i++){node u1 = G[i];for(int j = i + 1; j < G.size(); j++){node u2 = G[j];s1.insert(bfs(u1.x, u1.y, u2.x, u2.y));}}set<int>::iterator it;it = s1.begin();cout << *it << endl;continue;}for(int i = 0; i < n; i++){for(int j = 0; j < m; j++){if(str[i][j] == '#'){if(vis[i][j] == 1)s1.insert(spfa(i, j));elses2.insert(spfa(i, j));}}}set<int>::iterator it, is;it = s1.begin();is = s2.begin();int mxx = max(*it, *is);cout << mxx << endl;}return 0;
}