#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

//#define FILE 10
#define int int64_t

using namespace std;
using namespace __gnu_pbds;

template<typename T>
using orset = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename K>
using ormap = tree <T, K, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 1e2;
int ans = 0;
char a [N + 2] [N + 2];
bool visited [N + 2] [N + 2];
int n, m;

void dfs(pair <int, int> koord)
{
    if (a [koord.first] [koord.second] == 'G')
        ans++;
    if (a [koord.first] [koord.second + 1] != '#' && !visited [koord.first] [koord.second + 1])
    {
        visited [koord.first] [koord.second + 1] = 1;
        dfs({koord.first, koord.second + 1});
    }
    if (a [koord.first] [koord.second - 1] != '#' && !visited [koord.first] [koord.second - 1])
    {
        visited [koord.first] [koord.second - 1] = 1;
        dfs({koord.first, koord.second - 1});
    }
    if (a [koord.first + 1] [koord.second] != '#' && !visited [koord.first + 1] [koord.second])
    {
        visited [koord.first + 1] [koord.second] = 1;
        dfs({koord.first + 1, koord.second});
    }
    if (a [koord.first - 1] [koord.second] != '#' && !visited [koord.first - 1] [koord.second])
    {
        visited [koord.first - 1] [koord.second] = 1;
        dfs({koord.first - 1, koord.second});
    }
}

void solve()
{
    ans = 0;
    cin >> n >> m;
    for (int i = 0; i < n + 2; i++)
    {
        for (int j = 0; j < m + 2; j++)
            a [i] [j] = '#';
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
            cin >> a [i] [j];
    }
    if (a [n] [m] == 'B')
    {
        cout << "No\n";
        return;
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (a [i] [j] == 'B')
            {
                if (a [i + 1] [j] == '.')
                    a [i + 1] [j] = '#';
                if (a [i - 1] [j] == '.')
                    a [i - 1] [j] = '#';
                if (a [i] [j + 1] == '.')
                    a [i] [j + 1] = '#';
                if (a [i] [j - 1] == '.')
                    a [i] [j - 1] = '#';
            }
        }
    }
    int num = 0;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (a [i] [j] == 'G')
                num++;
        }
    }
    if (a [n] [m] != '#')
        dfs({n, m});
    if (num == ans)
        cout << "Yes\n";
    else
        cout << "No\n";

}

int32_t main(int32_t argc, char* argv[]) {
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    #ifdef FILE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
    int t = 1;
    cin >> t;
    while (t--)
        solve();
}