#include <bits/stdc++.h>
using namespace std;
const long double pi = 3.14159265358979323846;
long long mod1 = 1e9 + 7;
long long mod2 = 998244353;
long long mul(long long x, long long y) {
  return (1ll * (x % mod1) * (y % mod1));
}
long long modpow(long long x, long long y) {
  long long z = 1;
  while (y > 0) {
    if (y % 2) z = mul(z, x);
    x = mul(x, x);
    y /= 2;
  }
  return z;
}
long long power(long long x, long long y) {
  long long z = 1;
  while (y > 0) {
    if (y % 2) z = z * x;
    x = x * x;
    y /= 2;
  }
  return z;
}
long long gcd(long long a, long long b) {
  if (a < b) return gcd(b, a);
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long min(long long a, long long b) {
  if (a < b) return a;
  return b;
}
long long max(long long a, long long b) {
  if (a > b) return a;
  return b;
}
long long sq(long long a) {
  long long ans = (1ll * a * a);
  return ans;
}
long long n, m;
long long vis[51][51];
char a[51][51];
bool isvalid(long long x, long long y) {
  if (x < 0 || y < 0 || y > m - 1 || x > n - 1 || vis[x][y] || a[x][y] == '#')
    return false;
  return true;
}
long long chk, notg;
long long dx[4] = {0, 1, 0, -1};
long long dy[4] = {1, 0, -1, 0};
void dfs(long long x, long long y) {
  if (!isvalid(x, y)) return;
  vis[x][y] = 1;
  if (a[x][y] == 'G') {
    chk++;
  } else if (a[x][y] == 'B') {
    notg++;
  }
  for (long long i = 0; i < 4; i++) {
    long long newx = x + dx[i];
    long long newy = y + dy[i];
    if (isvalid(newx, newy)) {
      dfs(newx, newy);
    }
  }
}
void solve() {
  cin >> n >> m;
  long long cg = 0;
  vector<pair<long long, long long> > pos;
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < m; j++) {
      vis[i][j] = 0;
      cin >> a[i][j];
      if (a[i][j] == 'G') {
        cg++;
        pos.push_back({i, j});
      }
    }
  }
  if (cg == 0) {
    cout << "Yes"
         << "\n";
    return;
  }
  for (long long i = 0; i < n; i++) {
    for (long long j = 0; j < m; j++) {
      if (a[i][j] == 'B') {
        if (i > 0 && a[i - 1][j] != 'B' && a[i - 1][j] != 'G')
          a[i - 1][j] = '#';
        if (i < n - 1 && a[i + 1][j] != 'B' && a[i + 1][j] != 'G')
          a[i + 1][j] = '#';
        if (j < m - 1 && a[i][j + 1] != 'B' && a[i][j + 1] != 'G')
          a[i][j + 1] = '#';
        if (j > 0 && a[i][j - 1] != 'B' && a[i][j - 1] != 'G')
          a[i][j - 1] = '#';
      }
    }
  }
  chk = 0, notg = 0;
  dfs(n - 1, m - 1);
  if (chk == cg && notg == 0) {
    cout << "Yes\n";
  } else {
    cout << "No\n";
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  long long t = 1;
  cin >> t;
  while (t--) {
    solve();
  }
}
