#include <bits/stdc++.h>
using namespace std;
int n, m;
bool isvalid(int i, int j) {
  if ((i >= 0 && i < n) && (j >= 0 && j < m)) {
    return true;
  } else {
    return false;
  }
}
void solve() {
  cin >> n >> m;
  int countg = 0;
  vector<vector<char>> v(n, vector<char>(m));
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      cin >> v[i][j];
      if (v[i][j] == 'G') {
        countg++;
      }
    }
  }
  if (countg == 0) {
    cout << "YES"
         << "\n";
    return;
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (v[i][j] == 'B') {
        if (isvalid(i, j - 1) && v[i][j - 1] == '.') {
          v[i][j - 1] = '#';
        }
        if (isvalid(i, j + 1) && v[i][j + 1] == '.') {
          v[i][j + 1] = '#';
        }
        if (isvalid(i + 1, j) && v[i + 1][j] == '.') {
          v[i + 1][j] = '#';
        }
        if (isvalid(i - 1, j) && v[i - 1][j] == '.') {
          v[i - 1][j] = '#';
        }
      }
    }
  }
  if (v[n - 1][m - 1] == '#') {
    cout << "NO"
         << "\n";
    return;
  }
  queue<pair<int, int>> q;
  bool visited[n][m];
  memset(visited, false, sizeof(visited));
  q.push({n - 1, m - 1});
  visited[n - 1][m - 1] = true;
  while (!q.empty()) {
    pair<int, int> curr = q.front();
    q.pop();
    int i = curr.first;
    int j = curr.second;
    if (isvalid(i, j - 1) && !visited[i][j - 1] && v[i][j - 1] != '#') {
      q.push({i, j - 1});
      visited[i][j - 1] = true;
    }
    if (isvalid(i, j + 1) && !visited[i][j + 1] && v[i][j + 1] != '#') {
      q.push({i, j + 1});
      visited[i][j + 1] = true;
    }
    if (isvalid(i - 1, j) && !visited[i - 1][j] && v[i - 1][j] != '#') {
      q.push({i - 1, j});
      visited[i - 1][j] = true;
    }
    if (isvalid(i + 1, j) && !visited[i + 1][j] && v[i + 1][j] != '#') {
      q.push({i + 1, j});
      visited[i + 1][j] = true;
    }
  }
  int flag = 0;
  for (int k = 0; k < n; k++) {
    for (int l = 0; l < m; l++) {
      if ((v[k][l] == 'G' && !visited[k][l]) ||
          (v[k][l] == 'B' && visited[k][l])) {
        flag = 1;
        break;
      }
    }
  }
  if (flag == 1) {
    cout << "NO"
         << "\n";
  } else {
    cout << "YES"
         << "\n";
  }
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    solve();
  }
}
