#include <bits/stdc++.h>
using namespace std;
constexpr long long mod = 1000000007;
const long long INF = mod * mod;
const long double eps = 1e-12;
const long double pi = acos(-1.0);
void chmin(int &a, int b) { a = min(a, b); }
void chmax(int &a, int b) { a = max(a, b); }
long long mod_pow(long long a, long long n, long long m = mod) {
  a %= m;
  long long res = 1;
  while (n) {
    if (n & 1) res = res * a % m;
    a = a * a % m;
    n >>= 1;
  }
  return res;
}
struct modint {
  long long n;
  modint() : n(0) { ; }
  modint(long long m) : n(m) {
    if (n >= mod)
      n %= mod;
    else if (n < 0)
      n = (n % mod + mod) % mod;
  }
  operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) {
  a.n += b.n;
  if (a.n >= mod) a.n -= mod;
  return a;
}
modint operator-=(modint &a, modint b) {
  a.n -= b.n;
  if (a.n < 0) a.n += mod;
  return a;
}
modint operator*=(modint &a, modint b) {
  a.n = ((long long)a.n * b.n) % mod;
  return a;
}
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
  if (n == 0) return modint(1);
  modint res = (a * a) ^ (n / 2);
  if (n % 2) res = res * a;
  return res;
}
long long inv(long long a, long long p) {
  return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
const int max_n = 10001000;
modint fact[max_n], factinv[max_n];
void init_f() {
  fact[0] = modint(1);
  for (int i = 0; i < max_n - 1; i++) {
    fact[i + 1] = fact[i] * modint(i + 1);
  }
  factinv[max_n - 1] = modint(1) / fact[max_n - 1];
  for (int i = max_n - 2; i >= 0; i--) {
    factinv[i] = factinv[i + 1] * modint(i + 1);
  }
}
modint comb(int a, int b) {
  if (a < 0 || b < 0 || a < b) return 0;
  return fact[a] * factinv[b] * factinv[a - b];
}
int dx[4] = {0, 1, 0, -1};
int dy[4] = {1, 0, -1, 0};
char mp[50][50];
void solve() {
  int h, w;
  cin >> h >> w;
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) {
      cin >> mp[i][j];
    }
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) {
      if (mp[i][j] == 'B') {
        for (int d = 0; d < 4; d++) {
          int x = i + dx[d], y = j + dy[d];
          if (x < 0 || y < 0 || x == h || y == w) continue;
          if (mp[x][y] == 'G') {
            cout << "No\n";
            return;
          }
          if (mp[x][y] == '.') mp[x][y] = '#';
        }
      }
    }
  vector<vector<bool>> canr(h, vector<bool>(w, false));
  queue<pair<int, int>> q;
  if (mp[h - 1][w - 1] != '#') {
    canr[h - 1][w - 1] = true;
    q.push({h - 1, w - 1});
  }
  while (!q.empty()) {
    pair<int, int> p = q.front();
    q.pop();
    for (int d = 0; d < 4; d++) {
      int x = p.first + dx[d];
      int y = p.second + dy[d];
      if (x < 0 || y < 0 || x == h || y == w) continue;
      if (mp[x][y] != '#' && !canr[x][y]) {
        canr[x][y] = true;
        q.push({x, y});
      }
    }
  }
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) {
      if (mp[i][j] == 'G' && !canr[i][j]) {
        cout << "No\n";
        return;
      }
    }
  cout << "Yes\n";
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t;
  cin >> t;
  for (int i = 0; i < t; i++) solve();
  char nyaa;
  cin >> nyaa;
  return 0;
}
