#include <bits/stdc++.h>
using namespace std;
const int mods = 1e9 + 7;
const int maxn = 50 + 10;
const int N = 1e5 + 10;
const int E = 1e6 + 10;
long long n, p, m;
struct node {
  int x, y;
  node(int x, int y) : x(x), y(y) {}
};
vector<node> a;
bool good[maxn][maxn];
char h[maxn][maxn];
bool vis[maxn][maxn];
int b[4][2] = {0, 1, 0, -1, 1, 0, -1, 0};
int dfs(int x, int y) {
  vis[x][y] = 1;
  int res = true;
  for (int i = 0; i < 4; i++) {
    if ((x + b[i][0] > 0 && x + b[i][0] <= n) &&
        (y + b[i][1] > 0 && y + b[i][1] <= m)) {
      if (vis[x + b[i][0]][y + b[i][1]] || h[x + b[i][0]][y + b[i][1]] == '#')
        continue;
      if (h[x + b[i][0]][y + b[i][1]] == 'B') {
        if (h[x][y] == 'G') {
          res = false;
        } else {
          h[x][y] = '#';
          return res;
        }
      } else {
        res = min(res, dfs(x + b[i][0], y + b[i][1]));
      }
    }
  }
  return res;
}
int check(int x, int y) {
  if (h[x][y] == 'G') good[x][y] = 1;
  if (x == n && y == m) return true;
  vis[x][y] = 1;
  int res = 0;
  for (int i = 0; i < 4; i++) {
    if ((x + b[i][0] > 0 && x + b[i][0] <= n) &&
        (y + b[i][1] > 0 && y + b[i][1] <= m)) {
      if (vis[x + b[i][0]][y + b[i][1]] || h[x + b[i][0]][y + b[i][1]] == '#')
        continue;
      else {
        res = max(res, check(x + b[i][0], y + b[i][1]));
      }
    }
  }
  return res;
}
int main() {
  int t;
  cin >> t;
  while (t--) {
    memset(vis, 0, sizeof(vis));
    memset(good, 0, sizeof(good));
    a.clear();
    cin >> n >> m;
    for (long long i = 1; i <= (n); ++i) {
      for (long long j = 1; j <= (m); ++j) {
        cin >> h[i][j];
        if (h[i][j] == 'G') {
          a.push_back(node(i, j));
        }
      }
    }
    bool flg = 1;
    flg = dfs(n, m);
    if (!flg) {
      printf("No\n");
      continue;
    }
    for (int i = 0; i < a.size(); i++) {
      if (good[a[i].x][a[i].y]) continue;
      memset(vis, 0, sizeof(vis));
      flg = check(a[i].x, a[i].y);
      if (!flg) break;
    }
    if (flg) {
      printf("Yes\n");
    } else
      printf("No\n");
  }
}
