#include <bits/stdc++.h>
using namespace std;
const int x[4] = {-1, 0, +1, 0}, y[4] = {0, -1, 0, +1};
int t, n, m, G, B;
bool mark[55][55], g[55][55], b[55][55], check[55][55];
inline bool c(long long i, long long j) {
  return (i >= 0 and j >= 0 and n > i and m > j);
}
inline void dfs(long long i, long long j) {
  check[i][j] = 1;
  for (int k = 0; k < 4; k++)
    if (c(i + x[k], j + y[k]) and
        (!mark[i + x[k]][j + y[k]] or g[i + x[k]][j + y[k]]) and
        !check[i + x[k]][j + y[k]])
      dfs(i + x[k], j + y[k]);
}
string s;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> t;
  while (t--) {
    cin >> n >> m;
    G = B = 0;
    for (int i = 0; i < n; i++) {
      cin >> s;
      for (int j = 0; j < m; j++) {
        mark[i][j] = (s[j] != '.');
        g[i][j] = (s[j] == 'G');
        b[i][j] = (s[j] == 'B');
        G += g[i][j];
      }
    }
    if (G == 0) {
      cout << "YES\n";
      continue;
    }
    bool bad = b[n - 1][m - 1] or (s[m - 1] == '#');
    for (int i = 0; i < n; i++) {
      if (bad) break;
      for (int j = 0; j < m; j++) {
        if (bad) break;
        if (b[i][j]) {
          if (bad) break;
          for (int k = 0; k < 4; k++) {
            if (bad) break;
            if (c(i + x[k], j + y[k])) {
              if (g[i + x[k]][j + y[k]] or
                  (i + x[k] == n - 1 and j + y[k] == m - 1))
                bad = 1;
              mark[i + x[k]][j + y[k]] = 1;
            }
          }
        }
      }
    }
    if (bad) {
      cout << "NO\n";
      continue;
    }
    for (int p = 0; p < n; p++)
      for (int q = 0; q < m; q++) check[p][q] = 0;
    dfs(n - 1, m - 1);
    for (int i = 0; i < n; i++) {
      if (bad) break;
      for (int j = 0; j < m; j++) {
        if (bad) break;
        if (g[i][j] and !check[i][j]) bad = 1;
      }
    }
    if (bad) {
      cout << "NO\n";
      continue;
    }
    cout << "YES\n";
  }
}
