#include <bits/stdc++.h>
using namespace std;
int row[] = {1, 0, -1, 0};
int col[] = {0, 1, 0, -1};
bool vis[55][55];
void solve() {
  memset(vis, 0, sizeof vis);
  int n, m;
  cin >> n >> m;
  char arr[n + 5][m + 5];
  for (int i = 1; i <= n; ++i) {
    for (int j = 1; j <= m; ++j) {
      cin >> arr[i][j];
    }
  }
  for (int i = 1; i <= n; ++i) {
    for (int j = 1; j <= m; ++j) {
      if (arr[i][j] != 'B') continue;
      queue<pair<int, int>> q;
      q.push({i, j});
      vis[i][j] = 1;
      while (!q.empty()) {
        int x = q.front().first, y = q.front().second;
        q.pop();
        for (int k = 0; k < 4; ++k) {
          int baris = row[k] + x;
          int kolom = col[k] + y;
          if (baris >= 1 && baris <= n && kolom >= 1 && kolom <= m) {
            if (arr[baris][kolom] == '#')
              continue;
            else if (arr[baris][kolom] == '.') {
              arr[baris][kolom] = '#';
            } else if (arr[baris][kolom] == 'G') {
              cout << "NO" << '\n';
              return;
            } else if (arr[baris][kolom] == 'B' && !vis[baris][kolom]) {
              vis[baris][kolom] = 1;
              q.push({baris, kolom});
            }
          }
        }
      }
    }
  }
  memset(vis, 0, sizeof vis);
  queue<pair<int, int>> q;
  q.push({n, m});
  if (arr[n][m] == '#') {
    bool ok = 1;
    for (int i = 1; i <= n; ++i) {
      for (int j = 1; j <= m; ++j) {
        if (arr[i][j] == 'G') {
          ok = 0;
          break;
        }
      }
    }
    if (ok) {
      cout << "YES" << '\n';
      return;
    } else {
      cout << "NO" << '\n';
      return;
    }
  }
  while (!q.empty()) {
    int x = q.front().first, y = q.front().second;
    q.pop();
    for (int k = 0; k < 4; ++k) {
      int baris = row[k] + x;
      int kolom = col[k] + y;
      if (!vis[baris][kolom] && baris >= 1 && baris <= n && kolom >= 1 &&
          kolom <= m && arr[baris][kolom] != '#') {
        vis[baris][kolom] = 1;
        q.push({baris, kolom});
      }
    }
  }
  for (int i = 1; i <= n; ++i) {
    for (int j = 1; j <= m; ++j) {
      if (arr[i][j] == 'G' && !vis[i][j]) {
        cout << "NO" << '\n';
        return;
      }
      if (arr[i][j] == 'B' && vis[i][j]) {
        cout << "NO" << '\n';
        return;
      }
    }
  }
  cout << "YES" << '\n';
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  while (t--) solve();
}
