#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;
long long gcd(long long x, long long y) {
  if (y == 0)
    return x;
  else
    return gcd(y, x % y);
}
long long ksm(long long a, long long b) {
  long long r = 1;
  while (b) {
    if (b & 1) r = (r * a) % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return r;
}
void exgcd(long long a, long long b, long long &x, long long &y, long long &d) {
  if (!b)
    d = a, x = 1, y = 0;
  else
    exgcd(b, a % b, y, x, d), y -= a / b * x;
}
long long inv(long long a, long long p) {
  long long x, y, d;
  exgcd(a, p, x, y, d);
  x = (x % p + p) % p;
  return x;
}
inline int read() {
  char c = getchar();
  int x = 0, f = 1;
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = x * 10 + c - '0';
    c = getchar();
  }
  return x * f;
}
const int maxn = 1e5 + 100;
int n, m, k, t, dx[4] = {0, 0, 1, -1}, dy[4] = {1, -1, 0, 0};
char s[100][100], vis[100][100];
queue<pair<int, int>> q;
bool bfs(int x, int y, int num) {
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) vis[i][j] = 0;
  q.push(make_pair(x, y));
  vis[n][m] = 1;
  while (!q.empty()) {
    int x = q.front().first, y = q.front().second;
    q.pop();
    for (int i = 0; i < 4; i++) {
      int bx = x + dx[i], by = y + dy[i];
      if (bx < 1 || bx > n || by < 1 || by > m || vis[bx][by] ||
          s[bx][by] == 'B' || s[bx][by] == '#')
        continue;
      vis[bx][by] = 1;
      if (s[bx][by] == 'G') num--;
      q.push(make_pair(bx, by));
    }
  }
  return num == 0;
}
int main() {
  t = read();
  while (t--) {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%s", s[i] + 1);
    int ok = 1, num = 0;
    for (int i = 1; i <= n; i++)
      for (int j = 1; j <= m; j++) {
        if (s[i][j] == 'B') {
          if (s[i][j + 1] == 'G' || s[i][j - 1] == 'G' || s[i + 1][j] == 'G' ||
              s[i - 1][j] == 'G')
            ok = 0;
          else {
            if (s[i][j + 1] == '.') s[i][j + 1] = '#';
            if (s[i][j - 1] == '.') s[i][j - 1] = '#';
            if (s[i + 1][j] == '.') s[i + 1][j] = '#';
            if (s[i - 1][j] == '.') s[i - 1][j] = '#';
          }
        }
        if (s[i][j] == 'G') num++;
      }
    if (!num) {
      cout << "Yes\n";
      continue;
    }
    if (s[n - 1][m] == 'B' || s[n][m - 1] == 'B' || s[n - 1][m - 1] == 'B')
      ok = 0;
    if (ok) ok = bfs(n, m, num);
    if (ok)
      cout << "Yes\n";
    else
      cout << "No\n";
    for (int i = 1; i <= n; i++)
      for (int j = 1; j <= m; j++) s[i][j] = '\0', vis[i][j] = 0;
  }
}
