#include <bits/stdc++.h>
using namespace std;
char arr[51][51];
long long int n, m;
long long int dx[] = {0, 0, -1, 1};
long long int dy[] = {-1, 1, 0, 0};
bool solve() {
  vector<vector<bool>> vis(51, vector<bool>(51, false));
  vis[n - 1][m - 1] = true;
  queue<pair<long long int, long long int>> q;
  if (arr[n - 1][m - 1] != '#') {
    q.push(make_pair(n - 1, m - 1));
  }
  while (!q.empty()) {
    pair<long long int, long long int> p;
    p = q.front();
    q.pop();
    long long int x, y;
    for (long long int i = 0; i < 4; i++) {
      x = dx[i] + p.first;
      y = dy[i] + p.second;
      if (x >= 0 && y >= 0 && x < n && y < m) {
        if (!vis[x][y] && arr[x][y] != '#') {
          vis[x][y] = true;
          q.push(make_pair(x, y));
        }
      }
    }
  }
  for (long long int i = 0; i < n; i++) {
    for (long long int j = 0; j < m; j++) {
      if (arr[i][j] == 'G' && vis[i][j] == false) {
        return false;
      }
    }
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int t;
  cin >> t;
  while (t--) {
    long long int i, j, x = 0, y = 0, flag = 1, p, q;
    cin >> n >> m;
    for (i = 0; i < n; i++) {
      for (j = 0; j < m; j++) {
        cin >> arr[i][j];
      }
    }
    for (i = 0; i < n; i++) {
      for (j = 0; j < m; j++) {
        if (arr[i][j] == 'B') {
          for (long long int k = 0; k < 4; k++) {
            p = i + dx[k];
            q = j + dy[k];
            if (p >= 0 && q >= 0 && p < n && q < m) {
              if (arr[p][q] == 'G') {
                flag = 0;
              } else if (arr[p][q] != 'B') {
                arr[p][q] = '#';
              }
            }
          }
          arr[i][j] = '#';
        }
      }
    }
    bool res = solve();
    if (res == false) {
      flag = 0;
    }
    if (flag) {
      cout << "YES\n";
    } else {
      cout << "NO\n";
    }
  }
  return 0;
}
