#include <bits/stdc++.h>
using namespace std;
const long long N = 2 * 1e5 + 4;
long long add(long long a, long long b, long long m) {
  if (a < 0) a += m;
  if (b < 0) b += m;
  long long res = ((a % m) + (b % m)) % m;
  res %= m;
  return res;
}
long long mul(long long a, long long b, long long m) {
  if (a < 0) a += m;
  if (b < 0) b += m;
  long long res = ((a % m) * (b % m)) % m;
  res %= m;
  return res;
}
long long sub(long long a, long long b, long long m) {
  long long res = (a - b + m) % m;
  res %= m;
  return res;
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long t;
  cin >> t;
  while (t--) {
    long long n, m;
    cin >> n >> m;
    long long dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
    vector<string> second(n);
    for (long long i = 0; i < n; i++) {
      cin >> second[i];
    }
    auto valid = [&](long long x, long long y) {
      if (x >= n or x < 0) return false;
      if (y >= m or y < 0) return false;
      return true;
    };
    long long cntB = 0, cntG = 0;
    for (long long i = 0; i < n; i++) {
      for (long long j = 0; j < m; j++) {
        if (second[i][j] == 'B') {
          cntB++;
          for (long long k = 0; k < 4; k++) {
            long long ni = i + dir[k][0];
            long long nj = j + dir[k][1];
            if (valid(ni, nj) and second[ni][nj] == '.') {
              second[ni][nj] = '#';
            }
          }
        }
        if (second[i][j] == 'G') cntG++;
      }
    }
    long long tmp = cntB;
    long long vis[53][53];
    memset(vis, 0, sizeof(vis));
    function<void(long long, long long)> dfs = [&](long long x, long long y) {
      vis[x][y] = 1;
      for (long long i = 0; i < 4; i++) {
        long long ni = x + dir[i][0];
        long long nj = y + dir[i][1];
        if (!valid(ni, nj)) continue;
        if (vis[ni][nj] == 1 or second[ni][nj] == '#') continue;
        dfs(ni, nj);
      }
      return;
    };
    if (second[n - 1][m - 1] != '#') dfs(n - 1, m - 1);
    for (long long i = 0; i < n; i++) {
      for (long long j = 0; j < m; j++) {
        if (second[i][j] == 'G') {
          cntG -= vis[i][j];
        }
        if (second[i][j] == 'B') {
          cntB -= vis[i][j];
        }
      }
    }
    if (second[n - 1][m - 1] == '#' and cntG == 0) {
      cout << "Yes\n";
      continue;
    }
    if (cntG == 0 and cntB == tmp)
      cout << "Yes\n";
    else
      cout << "No\n";
  }
  return 0;
}
