#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <deque>
#include <climits>
#include <cmath>
#include <numeric>
#include <string>
#include <bitset>
#include <assert.h>
#include <iomanip>
using namespace std;
 
template <typename T>
using pqg = priority_queue<T, vector<T>, greater<T>>;
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
 
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
*/
/*
#include <bits/stdc++.h>
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define getrand(l, r) uniform_int_distribution<int>(l, r)(rng)
*/
 
const long long infl = 1e18 + 1;
const int inf = 1e9 + 1;
const int mod1 = 1e9 + 7;
const int mod2 = 998244353;
const long double eps = 1e-7;
const int mod = mod1;
 
int add(int a, int b) { return (a + b) % mod; }
int sub(int a, int b) { return (a - b + mod) % mod; }
int mul(int a, int b) { return (int)((long long)a * b % mod); }
int pwr(int a, int b = mod - 2)
{
	int res = 1;
	for(; b > 0; b >>= 1, a = mul(a, a))
		if(b & 1)
			res = mul(res, a);
	return res;
}
template <typename T>
bool chmax(T &a, T b)
{
	if(b > a)
	{
		a = b;
		return true;
	}
	return false;
}
template <typename T>
bool chmin(T &a, T b)
{
	if(b < a)
	{
		a = b;
		return true;
	}
	return false;
}

void solve()
{
	int n, m;
	cin >> n >> m;
	vector a(n, vector<char>());
	for(int i = 0; i < n; i++)
	{
		int cnt = 0;
		while(cnt < m)
		{
			char c;
			cin >> c;
			if(c == ' ')
				continue;
			a[i].push_back(c);
			cnt++;
		}
	}
	vector pref(n + 1, vector<int>(m + 1, 0));
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= m; j++)
			pref[i][j] = pref[i - 1][j] + pref[i][j - 1] - pref[i - 1][j - 1] + (a[i - 1][j - 1] == '+');
	auto query = [&](int i1, int j1, int i2, int j2) -> int
	{
		i1++, j1++, i2++, j2++;
		return pref[i2][j2] - pref[i2][j1 - 1] - pref[i1 - 1][j2] + pref[i1 - 1][j1 - 1];
	};
	int mx = 0;
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++)
		{
			int l = 0, r = min({i, j, n - i - 1, m - j - 1});
			while(l <= r)
			{
				int md = (l + r) / 2;
				bool can = true;
				can &= query(i - md, j, i, j) == md + 1;
				can &= query(i, j - md, i, j) == md + 1;
				can &= query(i, j, i + md, j) == md + 1;
				can &= query(i, j, i, j + md) == md + 1;
				if(can)
				{
					l = md + 1;
					chmax(mx, md * 4 + 1);
				}
				else
					r = md - 1;
			}
		}
	cout << mx;
}
 
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
 
	int t = 1;
	cin >> t;
 
	while (t--)
	{
		solve();
		cout << (t ? "\n" : "");
	}
}