#include <bits/stdc++.h>
using namespace std;
int n, m;
char arr[55][55];
int a1 = 0, a2 = 0, a3 = 0, a4 = 0;
vector<int> graph[3000];
int color[3000];
int d[3000];
void bfs(int s) {
  for (int i = 0; i <= m * n; i++) graph[i].clear();
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      int v = (i - 1) * (m) + j;
      if (i + 1 <= n && arr[i + 1][j] != '#') {
        graph[v].push_back(i * (m) + j);
      }
      if (i - 1 >= 1 && arr[i - 1][j] != '#')
        graph[v].push_back((i - 2) * (m) + j);
      if (j + 1 <= m && arr[i][j + 1] != '#')
        graph[v].push_back((i - 1) * (m) + j + 1);
      if (j - 1 >= 1 && arr[i][j - 1] != '#')
        graph[v].push_back((i - 1) * (m) + j - 1);
      color[v] = 0;
      d[v] = 100000;
    }
  }
  queue<int> q;
  q.push(s);
  color[s] = 1;
  if (arr[n][m] != '#')
    d[s] = 0;
  else
    d[s] = 100000;
  while (!q.empty()) {
    int j = q.front();
    for (int i = 0; i < graph[j].size(); i++) {
      if (color[graph[j][i]] == 0) {
        color[graph[j][i]] = 1;
        q.push(graph[j][i]);
        d[graph[j][i]] = d[j] + 1;
      }
    }
    q.pop();
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int t;
  cin >> t;
  while (t--) {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) cin >> arr[i][j];
    }
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
        if (arr[i][j] == 'B') {
          if (i + 1 <= n && arr[i + 1][j] == '.') arr[i + 1][j] = '#';
          if (i - 1 >= 1 && arr[i - 1][j] == '.') arr[i - 1][j] = '#';
          if (j + 1 <= m && arr[i][j + 1] == '.') arr[i][j + 1] = '#';
          if (j - 1 >= 1 && arr[i][j - 1] == '.') arr[i][j - 1] = '#';
        }
      }
    }
    bfs(n * m);
    int flag = 1;
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
        if (arr[i][j] == 'G' && d[(i - 1) * m + j] >= 100000) {
          flag = 0;
        }
        if (arr[i][j] == 'B' && d[(i - 1) * m + j] < 100000) {
          flag = 0;
        }
      }
    }
    if (flag)
      cout << "Yes" << endl;
    else
      cout << "No" << endl;
  }
}
