// created on : Sun Jun 07 2020
 
import java.io.*;
import java.util.*;

public class D {
    static boolean done[][];
    public static void main(String[] args) throws IOException {
        int t = in.nextInt();
        outer:
        while(t-->0){
            int n = in.nextInt();
            int m = in.nextInt();
            done = new boolean[n][m];
            char grid[][] = new char[n][m];
            for(int i = 0; i < n; i++){
                grid[i] = in.next().toCharArray();
            }

            // block all bad persons
            boolean blocked = blockBadPersons(grid, n, m);

            if(!blocked){
                println("No");
                continue;
            }
            
            // escape all good persons
            for(int i = 0; i < n; i++){
                for(int j = 0; j < m; j++){
                    if(grid[i][j] == 'G' && !done[i][j]){
                        boolean escaped = bfs(grid, i, j, n, m);
                        if(!escaped){
                            println("No");
                            continue outer;
                        }
                    }
                }
            }
            println("Yes");
        }
        
        in.close();
        out.close();
    }

    static int dx[] = {1, 0, -1, 0};
    static int dy[] = {0, -1, 0, 1};

    static boolean blockBadPersons(char grid[][], int n, int m){
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                if(grid[i][j] == 'B'){
                    for(int k = 0; k < 4; k++){
                        int x = i + dx[k];
                        int y = j + dy[k];
                        if(x >= 0 && x < n && y >= 0 && y < m){
                            if(grid[x][y] == 'G'){
                                return false;
                            }
                            else if(grid[x][y] == '.'){
                                grid[x][y] = '#';
                            }
                        }
                    }
                }
            }
        }
        return true;
    }

    static boolean bfs(char grid[][], int i, int j, int n, int m){
        Deque<int[]> q = new LinkedList<>();
        boolean visited[][] = new boolean[n][m];
        visited[i][j] = true;
        q.add(new int[]{i, j});
        while(!q.isEmpty()){
            int u[] = q.poll();
            if(u[0] == n - 1 && u[1] == m - 1){
                return true;
            }
            for(int k = 0; k < 4; k++){
                int x = u[0] + dx[k];
                int y = u[1] + dy[k];
                if(x >= 0 && x < n && y >= 0 && y < m && !visited[x][y]){
                    if(grid[x][y] == '#'){
                        continue;
                    }
                    else if(grid[x][y] == 'G'){
                        done[x][y] = true;
                    }
                    q.add(new int[]{x, y});
                    visited[x][y] = true;
                }
            }
        }
        return false;
    }

    static int MIN = Integer.MIN_VALUE;
    static int MAX = Integer.MAX_VALUE;
    static Reader in = new Reader();
    static PrintWriter out = new PrintWriter(System.out);

    static int[] readInt(int N) throws IOException { 
    	int arr[] = new int[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.nextInt(); 
    	} 
    	return arr;
    }
    
    static long[] readLong(int N) throws IOException { 
    	long arr[] = new long[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.nextLong(); 
    	} 
    	return arr;
    }
    
    static String[] readString(int N) throws IOException { 
    	String arr[] = new String[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.next(); 
    	} 
    	return arr;
    }
    
    static void print(Object O) {  
    	out.print(O); 
    }
    
    static void println(Object O) { 
    	out.println(O); 
    }
    
    static void println(int arr[]) { 
    	for(int i = 0; i < arr.length; i++){ 
    		print(arr[i] + " "); 
    	} 
    	println(""); 
    }
    
    static void debug(Object ... O) { 
    	for(Object obj: O){
    		System.out.print(obj + " ");
    	}
    	System.out.println();
    }
}

class Reader {
    BufferedReader reader;
    StringTokenizer tokenizer;

    Reader() {
        reader = new BufferedReader(new InputStreamReader(System.in));
        tokenizer = new StringTokenizer("");
    }

    String next() throws IOException {
        while (!tokenizer.hasMoreTokens() ) { 
            tokenizer = new StringTokenizer(reader.readLine()); 
        }
        return tokenizer.nextToken();
    }

    int nextInt() throws IOException { 
        return Integer.parseInt(next()); 
    }
    
    double nextDouble() throws IOException { 
        return Double.parseDouble(next());
    }
    
    long nextLong() throws IOException { 
        return Long.parseLong(next()); 
    }
    
    String nextLine() throws IOException { 
        return reader.readLine(); 
    }
    
    void close() throws IOException { 
        reader.close(); 
    }
}
