#include <bits/stdc++.h>
using namespace std;
const long long N = 100005;
const long long inf = 1e18;
long long n, m, i, j, k, t, u, v, color[55][55], nerk[55][55], qanakg, qanakb;
char a[55][55];
void dfs(long long x, long long y) {
  if (color[x][y - 1] != 1) {
    if (a[x][y - 1] == 'B')
      a[x][y] = '#';
    else {
      color[x][y - 1] = 1;
      dfs(x, y - 1);
    }
  }
  if (color[x][y + 1] != 1) {
    if (a[x][y + 1] == 'B')
      a[x][y] = '#';
    else {
      color[x][y + 1] = 1;
      dfs(x, y + 1);
    }
  }
  if (color[x - 1][y] != 1) {
    if (a[x - 1][y] == 'B')
      a[x][y] = '#';
    else {
      color[x - 1][y] = 1;
      dfs(x - 1, y);
    }
  }
  if (color[x + 1][y] != 1) {
    if (a[x + 1][y] == 'B')
      a[x][y] = '#';
    else {
      color[x + 1][y] = 1;
      dfs(x + 1, y);
    }
  }
}
void dfs1(long long x, long long y) {
  if (nerk[x][y - 1] != 1) {
    if (a[x][y - 1] == 'B')
      qanakb++;
    else {
      nerk[x][y - 1] = 1;
      dfs1(x, y - 1);
    }
  }
  if (nerk[x][y + 1] != 1) {
    if (a[x][y + 1] == 'B')
      qanakb++;
    else {
      nerk[x][y + 1] = 1;
      dfs1(x, y + 1);
    }
  }
  if (nerk[x - 1][y] != 1) {
    if (a[x - 1][y] == 'B')
      qanakb++;
    else {
      nerk[x - 1][y] = 1;
      dfs1(x - 1, y);
    }
  }
  if (nerk[x + 1][y] != 1) {
    if (a[x + 1][y] == 'B')
      qanakb++;
    else {
      nerk[x + 1][y] = 1;
      dfs1(x + 1, y);
    }
  }
}
void solve() {
  cin >> n >> m;
  qanakb = 0;
  long long cntg = 0;
  long long cntb = 0;
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= m; j++) {
      cin >> a[i][j];
      color[i][j] = 0;
      nerk[i][j] = 0;
      if (a[i][j] == 'G') cntg++;
      if (a[i][j] == 'B') cntb++;
      if (a[i][j] == '#') color[i][j] = 1;
    }
  }
  if (cntg == 0) {
    if (cntb == 0)
      cout << "Yes" << endl;
    else {
      if (a[n][m] == 'B')
        cout << "No" << endl;
      else
        cout << "Yes" << endl;
    }
    return;
  }
  for (i = 0; i <= n + 1; i++) {
    color[i][0] = 1;
    nerk[i][0] = 1;
    color[i][m + 1] = 1;
    nerk[i][m + 1] = 1;
    a[i][0] = '#';
    a[i][m + 1] = '#';
  }
  for (i = 0; i <= m + 1; i++) {
    color[0][i] = 1;
    nerk[0][i] = 1;
    color[n + 1][i] = 1;
    nerk[n + 1][i] = 1;
    a[0][i] = '#';
    a[n + 1][i] = '#';
  }
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= m; j++) {
      if (a[i][j] == 'G') {
        if (a[i][j + 1] == 'B' || a[i - 1][j] == 'B' || a[i + 1][j] == 'B' ||
            a[i][j - 1] == 'B') {
          cout << "No" << endl;
          return;
        }
      }
    }
  }
  color[n][m] = 1;
  nerk[n][m] = 1;
  dfs(n, m);
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= m; j++) {
      if (a[i][j] == '#') nerk[i][j] = 1;
    }
  }
  dfs1(n, m);
  if (qanakb != 0) {
    cout << "No" << endl;
    return;
  }
  for (i = 1; i <= n; i++) {
    for (j = 1; j <= m; j++) {
      if (a[i][j] == 'G' && nerk[i][j] == 0) {
        cout << "No" << endl;
        return;
      }
    }
  }
  cout << "Yes" << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
