#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
long long int dx[4] = {1, 0, -1, 0};
long long int dy[4] = {0, 1, 0, -1};
vector<vector<long long int>> vis(51, vector<long long int>(51, 0));
vector<vector<char>> grid(51, vector<char>(51));
bool is_valid(long long int x, long long int y, long long int n,
              long long int m) {
  if (x < 0 || y < 0 || x > n - 1 || y > m - 1) return false;
  return true;
}
bool dfs(long long int x, long long int y, long long int n, long long int m) {
  if (vis[x][y] == 1) {
    return false;
  }
  vis[x][y] = 1;
  if (x == n - 1 && y == m - 1) {
    return true;
  }
  for (long long int i = 0; i < 4; i++) {
    long long int cx = x + dx[i];
    long long int cy = y + dy[i];
    if (is_valid(cx, cy, n, m)) {
      if (grid[cx][cy] != '#') {
        if (dfs(cx, cy, n, m)) {
          return true;
        }
      }
    }
  }
  return false;
}
void solve() {
  long long int n = 0, m = 0;
  cin >> n >> m;
  for (long long int i = 0; i < n; i++) {
    for (long long int j = 0; j < m; j++) {
      cin >> grid[i][j];
    }
  }
  for (long long int i = 0; i < n; i++) {
    for (long long int j = 0; j < m; j++) {
      if (grid[i][j] == 'B') {
        for (long long int k = 0; k < 4; k++) {
          long long int x = i + dx[k];
          long long int y = j + dy[k];
          if (is_valid(x, y, n, m)) {
            if (grid[x][y] == 'G') {
              cout << "No\n";
              return;
            } else if (grid[x][y] == '.') {
              grid[x][y] = '#';
            }
          }
        }
      }
    }
  }
  for (long long int i = 0; i < n; i++) {
    for (long long int j = 0; j < m; j++) {
      if (grid[i][j] == 'G') {
        for (long long int k = 0; k < n; k++) {
          for (long long int l = 0; l < m; l++) {
            vis[k][l] = 0;
          }
        }
        if (!dfs(i, j, n, m)) {
          cout << "No\n";
          return;
        }
      }
    }
  }
  cout << "Yes\n";
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie();
  long long int t;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
