#include <bits/stdc++.h>
using namespace std;
long long int n, m;
long long int dp[50][50];
bool tr[50][50];
void find(int i, int j) {
  if ((i < 0 || i > n - 1) || (j < 0 || j > m - 1)) return;
  tr[i][j] = true;
  if (i - 1 >= 0 && dp[i - 1][j] != 3 && tr[i - 1][j] == false) find(i - 1, j);
  if (j - 1 >= 0 && dp[i][j - 1] != 3 && tr[i][j - 1] == false) {
    find(i, j - 1);
  }
  if (j + 1 < m && dp[i][j + 1] != 3 && tr[i][j + 1] == false) {
    find(i, j + 1);
  }
  if (i + 1 < n && dp[i + 1][j] != 3 && tr[i + 1][j] == false) {
    find(i + 1, j);
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int t;
  cin >> t;
  while (t--) {
    memset(tr, false, sizeof(tr));
    cin >> n >> m;
    string s[n];
    for (int i = 0; i < n; i++) cin >> s[i];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if (s[i][j] == 'B')
          dp[i][j] = 2;
        else if (s[i][j] == 'G')
          dp[i][j] = 1;
        else if (s[i][j] == '#')
          dp[i][j] = 3;
        else
          dp[i][j] = 0;
      }
    }
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if (dp[i][j] == 2) {
          if (i - 1 >= 0 && dp[i - 1][j] == 0) dp[i - 1][j] = 3;
          if (i + 1 < n && dp[i + 1][j] == 0) dp[i + 1][j] = 3;
          if (j - 1 >= 0 && dp[i][j - 1] == 0) dp[i][j - 1] = 3;
          if (j + 1 < m && dp[i][j + 1] == 0) dp[i][j + 1] = 3;
        }
      }
    }
    if (dp[n - 1][m - 1] != 3) find(n - 1, m - 1);
    long long int flag = 0;
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if ((dp[i][j] == 2 && tr[i][j] == true) ||
            (dp[i][j] == 1 && tr[i][j] == false)) {
          flag = 1;
          goto k;
        }
      }
    }
  k:;
    if (flag)
      cout << "No\n";
    else
      cout << "Yes\n";
  }
}
