#include <bits/stdc++.h>
using namespace std;
int n, m;
char ar[51][51];
bool flag = false;
vector<vector<bool>> vis;
void dfs(int i, int j, char ch) {
  if (ar[i][j] == '#' || ar[i][j] == ch || vis[i][j]) return;
  vis[i][j] = true;
  if (ar[i][j] == 'G') ar[i][j] = '.';
  if (i == n - 1 && j == m - 1) {
    flag = true;
    return;
  }
  if (i < n - 1) dfs(i + 1, j, ch);
  if (i > 0) dfs(i - 1, j, ch);
  if (j < m - 1) dfs(i, j + 1, ch);
  if (j > 0) dfs(i, j - 1, ch);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int t;
  cin >> t;
  vector<vector<bool>> d(51, vector<bool>(51, false));
  while (t--) {
    flag = false;
    bool ans = true;
    cin >> n >> m;
    for (int i = 0; i < n; i++)
      for (int j = 0; j < m; j++) cin >> ar[i][j];
    for (int i = 0; i < n; i++)
      for (int j = 0; j < m; j++)
        if (ar[i][j] == 'B') {
          if (i != 0)
            if (ar[i - 1][j] == '.')
              ar[i - 1][j] = '#';
            else if (ar[i - 1][j] == 'G')
              ans = false;
          if (i != n - 1)
            if (ar[i + 1][j] == '.')
              ar[i + 1][j] = '#';
            else if (ar[i + 1][j] == 'G')
              ans = false;
          if (j != 0)
            if (ar[i][j - 1] == '.')
              ar[i][j - 1] = '#';
            else if (ar[i][j - 1] == 'G')
              ans = false;
          if (j != m - 1)
            if (ar[i][j + 1] == '.')
              ar[i][j + 1] = '#';
            else if (ar[i][j + 1] == 'G')
              ans = false;
        }
    if (ans)
      for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) {
          if (ar[i][j] == 'G') {
            vis = d;
            dfs(i, j, 'B');
            if (!flag) {
              ans = false;
              break;
            }
            flag = false;
          }
        }
    if (ans)
      cout << "YES\n";
    else
      cout << "NO\n";
  }
  return 0;
}
