#include <bits/stdc++.h>
using namespace std;
template <class c>
struct rge {
  c b, e;
};
template <class c>
rge<c> range(c i, c j) {
  return rge<c>{i, j};
}
template <class c>
auto dud(c* x) -> decltype(cerr << *x, 0);
template <class c>
char dud(...);
struct debug {
  template <class c>
  debug& operator<<(const c&) {
    return *this;
  }
};
vector<char*> tokenizer(const char* args) {
  char* token = new char[111];
  strcpy(token, args);
  token = strtok(token, ", ");
  vector<char*> v({token});
  while (token = strtok(NULL, ", ")) v.push_back(token);
  return reverse(v.begin(), v.end()), v;
}
void debugg(vector<char*> args) { cerr << "\b\b "; }
template <typename Head, typename... Tail>
void debugg(vector<char*> args, Head H, Tail... T) {
  debug() << " [" << args.back() << ": " << H << "] ";
  args.pop_back();
  debugg(args, T...);
}
int mod = 998244353;
const int MX = 0x3f3f3f3f;
int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1};
int flag, cnt, vis[51][51], n, m;
char a[51][51];
void dfs(int i, int j) {
  vis[i][j] = 1;
  if (i == n - 1 && j == m - 1) {
    flag = 1;
  }
  if (a[i][j] == 'G') {
    cnt++;
  }
  for (int k = 0; k <= 3; k++) {
    int x = i + dx[k], y = j + dy[k];
    if (x >= 0 && x < n && y >= 0 && y < m)
      if (!vis[x][y] && a[x][y] != '#') dfs(x, y);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  while (t--) {
    int i, j;
    cin >> n >> m;
    int num = 0;
    memset(vis, 0, sizeof(vis));
    for (i = 0; i <= n - 1; i++)
      for (j = 0; j <= m - 1; j++) {
        cin >> a[i][j];
        if (a[i][j] == 'G') num++;
      }
    for (i = 0; i <= n - 1; i++) {
      for (j = 0; j <= m - 1; j++) {
        if (a[i][j] == 'B') {
          for (int k = 0; k <= 3; k++) {
            int x = i + dx[k], y = j + dy[k];
            if (x >= 0 && x < n && y >= 0 && y < m) {
              if (a[x][y] == 'G') {
                cout << "NO\n";
                goto AA;
              }
              if (a[x][y] != 'B') a[x][y] = '#';
            }
          }
        }
      }
    }
    flag = 1;
    cnt = 0;
    for (i = 0; i <= n - 1; i++) {
      for (j = 0; j <= m - 1; j++) {
        if (a[i][j] == 'G') {
          flag = 0;
          dfs(i, j);
          goto BB;
        }
      }
    }
  BB:;
    if (!flag || cnt != num)
      cout << "NO\n";
    else
      cout << "YES\n";
  AA:;
  }
  return 0;
}
