/// Bismillahir Rahmanir Rahim
/* Mohammad Morsalin
   Dept of ICE, NSTU
*/
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ll long long
#define pb push_back
#define mp make_pair
#define endl "\n"
#define int long long
#define f0(n) for(int i=0;i<n;i++)
#define ms(x) memset(x,0,sizeof(x))
#define ms2d(x,m,n) memset(x, 0, sizeof(x[0][0]) * m * n)
#define uniq(vec) vec.resize(distance(vec.begin(),unique(vec.begin(),vec.end())))
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define pi pair<int,int>
#define tc(t) int t;cin>>t;while(t--)
#define bits(n) __builtin_popcount(n)
#define maxpq priority_queue<int>
#define minpq priority_queue<int, vector<int>, greater<int> >
#define ins insert
#define ALL(v) v.begin(),v.end()
#define highest(x) numeric_limits<x>::max()
#define lowest(x) numeric_limits<x>::min()
#define Inf INFINITY
#define minv(v) *min_element(v.begin(),v.end())
#define maxv(v) *max_element(v.begin(),v.end())
#define fi first
#define se second
#define PI acos(-1)
#define sz(a) (int)a.size();
#define IOS ios::sync_with_stdio(false);
using namespace std;
int gcd(int a, int b) { if (a == 0) return b; return gcd(b % a, a);}
typedef tree<pair<int, int>,null_type,less<pair<int, int>>,rb_tree_tag,tree_order_statistics_node_update> ordered_multiset;
int dx8[] = {0, 0, 1, 1, 1, -1, -1, -1};
int dy8[] = {1,-1, 1, -1, 0, 0, -1, 1};
int dx4[] = {0, 0, 1, -1};
int dy4[] = {1, -1, 0, 0};
const long long MOD = 1000000007;
double sq(double x) {return x*x;}
template<typename T>inline T Bigmod(T base, T power, T MOD){
    T ret=1;
    while(power)
    {
        if(power & 1)ret=(ret*base)%MOD;
        base=(base*base)%MOD;
        power>>=1;
    }
    return ret;
}

bool sortinrev(const pair<int,int> &a,
               const pair<int,int> &b)
{
       return (a.first > b.first);
}
signed main()
{
    IOS
    int t;
    cin>>t;
    while(t--){
        int n,m;
        cin>>n>>m;
        string s[n];
        for(int i=0;i<n;i++){
            cin>>s[i];
        }
         for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(s[i][j]=='B'){
                    if(i<n-1 && s[i+1][j]=='.'){
                        s[i+1][j]='#';
                    }
                    if(i>0 && s[i+1][j]=='.'){
                        s[i-1][j]='#';
                    }
                    if(j<m-1 && s[i][j+1]=='.'){
                        s[i][j+1]='#';
                    }
                    if(j>0 && s[i][j-1]=='.'){
                        s[i][j-1]='#';
                    }
                }
            }
        }
        bool allgood=1;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(s[i][j]=='G'){
                    stack<pi>st;
                    bool got=0;
                    st.push(mp(i,j));
                    int vis[n][m];
                    ms2d(vis,n,m);
                    while(!st.empty()){
                        int x=st.top().fi;
                        int y=st.top().se;
                        st.pop();
                        if(x==n-1 && y==m-1){
                            got=1;
                        }
                        vis[x][y]=1;
                        for(int i=0;i<4;i++){
                            int nx=x+dx4[i];
                            int ny=y+dy4[i];
                            if((nx>=0 && nx<n) && (ny>=0 && ny<m) && s[nx][ny]!='#'&& vis[nx][ny]==0){
                                st.push(mp(nx,ny));
                            }
                        }
                    }
                    if(!got){
                        allgood=0;
                        break;
                    }
                }
            }
        }
        if(allgood){
            cout << "YES\n";
        }
        else{
            cout << "NO\n";
        }
    }
    return 0;
}
///Alhamdulillah

