#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
template <class T, class S>
ostream &operator<<(ostream &o, const pair<T, S> &p) {
  return o << '(' << p.first << ", " << p.second << ')';
}
template <template <class, class...> class T, class... A>
typename enable_if<!is_same<T<A...>, string>(), ostream &>::type operator<<(
    ostream &o, T<A...> V) {
  o << '[';
  for (auto a : V) o << a << ", ";
  return o << ']';
}
string grid[110];
long long int n, m, dx[4] = {0, 0, -1, 1}, dy[4] = {-1, 1, 0, 0};
bool used[110][110];
void dfs(long long int i, long long int j) {
  used[i][j] = true;
  for (long long int k = 0; k < 4; k++) {
    long long int i2 = i + dx[k], j2 = j + dy[k];
    if ((i2 >= 0 && j2 >= 0 && i2 < n && j2 < m) && !used[i2][j2] &&
        grid[i2][j2] != '#')
      dfs(i2, j2);
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long long int tc;
  cin >> tc;
  while (tc--) {
    cin >> n >> m;
    for (long long int i = 0; i < n; i++) cin >> grid[i];
    for (long long int i = 0; i < n; i++)
      for (long long int j = 0; j < m; j++) used[i][j] = false;
    for (long long int i = 0; i < n; i++)
      for (long long int j = 0; j < m; j++)
        if (grid[i][j] == 'B')
          for (long long int k = 0; k < 4; k++) {
            long long int i2 = i + dx[k], j2 = j + dy[k];
            if ((i2 >= 0 && j2 >= 0 && i2 < n && j2 < m) && grid[i2][j2] == '.')
              grid[i2][j2] = '#';
          }
    if (grid[n - 1][m - 1] != '#') dfs(n - 1, m - 1);
    string ans = "Yes\n";
    for (long long int i = 0; i < n; i++)
      for (long long int j = 0; j < m; j++)
        if (used[i][j] && grid[i][j] == 'B')
          ans = "No\n";
        else if (!used[i][j] && grid[i][j] == 'G')
          ans = "No\n";
    cout << ans;
  }
}
