#include <bits/stdc++.h>
using namespace std;
const int N = 100;
char a[N][N];
bool mark[N][N];
int n, m, dx[] = {1, 0, -1, 0}, dy[] = {0, -1, 0, 1};
queue<pair<int, int> > q;
bool isInside(int x, int y) { return (x >= 0 && y >= 0 && x < n && y < m); }
void BFS() {
  while (!q.empty()) {
    auto u = q.front();
    q.pop();
    for (int i = 0; i < 4; i++) {
      int x = dx[i] + u.first, y = dy[i] + u.second;
      if (isInside(x, y) && a[x][y] != '#' && !mark[x][y]) {
        q.push(make_pair(x, y));
        mark[x][y] = true;
      }
    }
  }
  return;
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int t;
  cin >> t;
  while (t--) {
    cin >> n >> m;
    bool flag = true;
    for (int i = 0; i < n; i++)
      for (int j = 0; j < m; j++) cin >> a[i][j];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        mark[i][j] = false;
        if (a[i][j] == 'B') {
          for (int k = 0; k < 4; k++) {
            int x = i + dx[k];
            int y = j + dy[k];
            if (isInside(x, y)) {
              if (a[x][y] == 'G') {
                flag = false;
              } else if (a[x][y] == '.')
                a[x][y] = '#';
            }
          }
        }
      }
    }
    if (a[n - 1][m - 1] != '#') {
      q.push(make_pair(n - 1, m - 1));
      mark[n - 1][m - 1] = true;
    }
    BFS();
    for (int i = n - 1; i >= 0; i--)
      for (int j = m - 1; j >= 0; j--)
        if ((a[i][j] == 'G' && mark[i][j] == false) ||
            (a[i][j] == 'B' && mark[i][j] == true))
          flag = false;
    if (flag)
      cout << "Yes" << endl;
    else
      cout << "No" << endl;
  }
  return 0;
}
