#include <bits/stdc++.h>
using namespace std;
char graph[50][50];
int path[50][50];
int order = 0;
int count_G = 0;
void spread(int x, int y, int row, int col) {
  if (x < 0 || y < 0 || x >= row || y >= col) {
    return;
  }
  if (path[x][y] == 1) {
    return;
  }
  path[x][y] = 1;
  if (graph[x][y] == '#') {
    return;
  }
  if (graph[x][y] == 'G') {
    ++count_G;
  }
  spread(x - 1, y, row, col);
  spread(x, y - 1, row, col);
  spread(x + 1, y, row, col);
  spread(x, y + 1, row, col);
}
void solve() {
  count_G = 0;
  int row, col;
  vector<pair<int, int> > good, bad;
  cin >> row >> col;
  for (int r = 0; r < row; ++r) {
    for (int c = 0; c < col; ++c) {
      cin >> graph[r][c];
      path[r][c] = 0;
      if (graph[r][c] == 'G') {
        good.push_back(pair<int, int>(r, c));
      } else if (graph[r][c] == 'B') {
        bad.push_back(pair<int, int>(r, c));
      }
    }
  }
  if (good.size() == 0) {
    cout << "Yes\n";
    return;
  }
  for (int i = 0; i < bad.size(); ++i) {
    int x = bad[i].first, y = bad[i].second;
    if (x > 0) {
      if (graph[x - 1][y] == 'G') {
        cout << "No\n";
        return;
      }
      if (graph[x - 1][y] == '.') {
        graph[x - 1][y] = '#';
      }
    }
    if (y > 0) {
      if (graph[x][y - 1] == 'G') {
        cout << "No\n";
        return;
      }
      if (graph[x][y - 1] == '.') {
        graph[x][y - 1] = '#';
      }
    }
    if (x < row - 1) {
      if (graph[x + 1][y] == 'G') {
        cout << "No\n";
        return;
      }
      if (graph[x + 1][y] == '.') {
        graph[x + 1][y] = '#';
      }
    }
    if (y < col - 1) {
      if (graph[x][y + 1] == 'G') {
        cout << "No\n";
        return;
      }
      if (graph[x][y + 1] == '.') {
        graph[x][y + 1] = '#';
      }
    }
  }
  if (graph[row - 1][col - 1] == '#') {
    cout << "No\n";
    return;
  }
  spread(row - 1, col - 1, row, col);
  if (count_G == good.size()) {
    cout << "Yes\n";
  } else {
    cout << "No\n";
  }
}
int main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(0);
  ;
  int num_test;
  cin >> num_test;
  for (int i = 0; i < num_test; ++i) {
    solve();
  }
}
