#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC target("avx")
bool RELAXED = false;
template <int, typename T>
struct MINMAX {
  T val;
  MINMAX(T val) : val(val) {}
};
template <typename T>
MINMAX<1, T> MAX(T val) {
  return MINMAX<1, T>(val);
};
template <typename T>
MINMAX<2, T> MIN(T val) {
  return MINMAX<2, T>(val);
};
template <typename T, typename U>
inline T& operator|=(T& lhs, MINMAX<1, U> rhs) {
  return lhs = (rhs.val > lhs ? (RELAXED = true, rhs.val)
                              : (RELAXED = false, lhs));
}
template <typename T, typename U>
inline T& operator|=(T& lhs, MINMAX<2, U> rhs) {
  return lhs = (rhs.val < lhs ? (RELAXED = true, rhs.val)
                              : (RELAXED = false, lhs));
}
template <typename T, typename U>
istream& operator>>(istream& in, pair<T, U>& p) {
  in >> p.first >> p.second;
  return in;
}
template <typename T>
inline vector<T> READ(int n) {
  vector<T> vec(n);
  for (int i = 0; i < int(n); i++) cin >> vec[i];
  return vec;
}
template <typename T>
using min_heap = priority_queue<T, vector<T>, greater<T> >;
vector<string> grid;
int n, m;
int rb, rg;
set<pair<int, int> > visited;
void block(int r, int c) {
  if (r < 0 || r >= n) return;
  if (c < 0 || c >= m) return;
  if (grid[r][c] == '.') grid[r][c] = '#';
}
void dfs(int r, int c) {
  if (r < 0 || r >= n) return;
  if (c < 0 || c >= m) return;
  if (visited.count({r, c})) return;
  visited.insert({r, c});
  if (grid[r][c] == '#') return;
  if (grid[r][c] == 'B') rb++;
  if (grid[r][c] == 'G') rg++;
  dfs(r - 1, c);
  dfs(r + 1, c);
  dfs(r, c - 1);
  dfs(r, c + 1);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  cout << fixed << setprecision(12);
  int T;
  cin >> T;
  while (T--) {
    grid.clear();
    rb = 0, rg = 0;
    visited.clear();
    cin >> n >> m;
    grid = READ<string>(n);
    int bad = 0, good = 0;
    for (int i = 0; i < int(n); i++) {
      bad += count((grid[i]).begin(), (grid[i]).end(), 'B');
      good += count((grid[i]).begin(), (grid[i]).end(), 'G');
    }
    for (int i = 0; i < int(n); i++) {
      for (int j = 0; j < int(m); j++) {
        if (grid[i][j] == 'B') {
          block(i - 1, j);
          block(i + 1, j);
          block(i, j - 1);
          block(i, j + 1);
        }
      }
    }
    dfs(n - 1, m - 1);
    if (rb > 0 || rg < good)
      cout << "No" << endl;
    else
      cout << "Yes" << endl;
  }
}
