#include <bits/stdc++.h>
#define pi pair<int, int>
#define x first
#define y second
using namespace std;
int main()
{
int t;
cin>>t;
std::vector<string> re;
for(int i=0;i<t;i++){
int n,m;
cin>>n>>m;
char ar[n][m];
bool v[n][m];
int numG,numB;
for(int j=0;j<n;j++){
for(int k=0;k<m;k++){
v[j][k] = false;
cin>>ar[j][k];
if(ar[j][k]=='G') numG++;
else if(ar[j][k]=='B') numB++;
else if(ar[j][k]=='#') v[j][k] = true;
}
}
// cout<<"\n-----------------------------------------------------\n";
// for(int j=0;j<n;j++){
// cout<<"\n";
// for(int k=0;k<m;k++){
// cout<<" "<<ar[j][k];
// }
// }
bool needBreak = false;
if(numG==0) {
re.push_back("Yes");
needBreak = true;
continue;
}
int dx[] = {0,0,1,-1};
int dy[] = {1,-1,0,0};
for(int j=0;j<n;j++){
for(int k=0;k<m;k++){
if(ar[j][k]=='B'){
if(needBreak) break;
v[j][k] = true;
for(int h=0;h<4;h++){
//cout<<"\n j "<<j<<" k "<<k <<" h "<<h;
int x = j+dx[h];
int y = k+dy[h];
if(x<0 || y<0||x>=n||y>=m) continue;
//cout<<"\n --> x "<<x<<" y "<<y;
if(ar[x][y]=='G') {
needBreak = true;
re.push_back("No");
//cout<<"\n -->break: x "<<x<<" y "<<y;
break;
} else if(ar[x][y]=='.') {
ar[x][y]='#';
v[x][y] = true;
}
}
}
}
}
if(needBreak) continue;
else {
if(ar[n-1][m-1]=='#'){
re.push_back("No");
continue;
}
int count = 0;
std::queue<pi> q ;
q.push({n-1, m-1});
v[n-1][m-1] = true;
while(!q.empty()){
pi top = q.front();
q.pop();
for(int h=0;h<4;h++){
//cout<<"\n j "<<j<<" k "<<k <<" h "<<h;
int x = top.x+dx[h];
int y = top.y+dy[h];
if(x<0 || y<0||x>=n||y>=m || v[x][y]) continue;
//cout<<"\n --> x "<<x<<" y "<<y;
q.push({x,y});
v[x][y] = true;
if(ar[x][y]=='G') {
count++;
//cout<<"\n -->break: x "<<x<<" y "<<y;
}
}
}
if(count>=numG) re.push_back("Yes");
else re.push_back("No");
}
}
for(auto s:re){
cout<<s<<"\n";
}
return 0;
}
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