import java.io.*;
import java.util.*;
import java.math.*;

//Mann Shah [ DAIICT ].

public class Main {
	static long mod = (long) (1e9+7);
	static InputReader in;
    static PrintWriter out;
    static Debugger deb;  

    public static boolean isv(int i,int j) {
    		return (i<n && i>=0 && j<m && j>=0);
    }
    
    public static void dfs(int i, int j, boolean[][] vis, char[][] s) {
    		
    		if(s[i][j]=='#')
    			return;
    	
    		if(isv(i+1,j) && s[i+1][j]=='B') return;
    		if(isv(i-1,j) && s[i-1][j]=='B') return;
    		if(isv(i,j+1) && s[i][j+1]=='B') return;
    		if(isv(i,j-1) && s[i][j-1]=='B') return;
    		
    		if(s[i][j]=='G')  count++;
    		
    		vis[i][j] = true;
    		
    		if(isv(i+1,j) && !vis[i+1][j])
    			dfs(i+1,j,vis,s);
    		if(isv(i-1,j) && !vis[i-1][j])
    			dfs(i-1,j,vis,s);
    		if(isv(i,j+1) && !vis[i][j+1])
    			dfs(i,j+1,vis,s);
    		if(isv(i,j-1) && !vis[i][j-1])
    			dfs(i,j-1,vis,s);
			
	}
    public static int n,m,count=0;
            
    	public static void main(String args[] ) throws NumberFormatException, IOException  {
			
		in = new InputReader(System.in);
	    out = new PrintWriter(System.out);
	    deb = new Debugger();
	   
	    	int T = in.nextInt();
	    	while(T-->0) {
	    		n = in.nextInt();
	    		m = in.nextInt();
	    		char[][] s = new char[n][m];
	    		for(int i=0;i<n;i++) {
	    			s[i] = in.readString().toCharArray();
	    		}
	    		int cg=0;
	    		for(int i=0;i<n;i++) {
	    			for(int j=0;j<m;j++) {
	    				if(s[i][j]=='G') {
	    					cg++;
	    				}
	    			}
	    		}
	    		boolean[][] vis = new boolean[n][m];
	    		int flag=0;
	    		
	    		dfs(n-1,m-1,vis,s);
	    		
	    		if(count == cg) {
	    			out.println("Yes");
	    		}
	    		else {
	    			out.println("No");
	    		}
	    		
	    		count=0;
	    	}

	    out.close();
	}


/* TC space


 */	
		static class InputReader
	    {
	        private final InputStream stream;
	        private final byte[] buf = new byte[8192];
	        private int curChar, snumChars;
	        private SpaceCharFilter filter;

	        public InputReader(InputStream stream){
	                this.stream = stream;
	        }
	        public int snext(){
                if (snumChars == -1) throw new InputMismatchException();
                if (curChar >= snumChars){
                        curChar = 0;
                        try{
                                snumChars = stream.read(buf);
                        } catch (IOException e){
                                throw new InputMismatchException();
                        }
                        if (snumChars <= 0)
                                return -1;
                }
                return buf[curChar++];
	        }

	        public int nextInt(){
	                int c = snext();
	                while (isSpaceChar(c)){
	                    c = snext();
	                }
	                int sgn = 1;
	                if (c == '-'){
                        sgn = -1;
                        c = snext();
	                }
	                int res = 0;
	                do{
                        if (c < '0' || c > '9')
                                throw new InputMismatchException();
                        res *= 10;
                        res += c - '0';
                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public long nextLong()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                int sgn = 1;
	                if (c == '-')
	                {
	                        sgn = -1;
	                        c = snext();
	                }
	                long res = 0;
	                do
	                {
	                        if (c < '0' || c > '9')
	                                throw new InputMismatchException();
	                        res *= 10;
	                        res += c - '0';
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res * sgn;
	        }

	        public int[] nextIntArray(int n)
	        {
	                int a[] = new int[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextInt();
	                }
	                return a;
	        }

	        public long[] nextLongArray(int n)
	        {
	                long a[] = new long[n];
	                for (int i = 0; i < n; i++)
	                {
	                        a[i] = nextLong();
	                }
	                return a;
	        }
	        
	        public ArrayList<Integer> nextArrayList(int n){
	        			ArrayList<Integer> x = new ArrayList<Integer>();
	        			for(int i=0;i<n;i++) {
	        				int v = in.nextInt();
	        				x.add(v);
	        			}
	        			return x;
	        }

	        public String readString()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                {
	                        c = snext();
	                }
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isSpaceChar(c));
	                return res.toString();
	        }

	        public String nextLine()
	        {
	                int c = snext();
	                while (isSpaceChar(c))
	                        c = snext();
	                StringBuilder res = new StringBuilder();
	                do
	                {
	                        res.appendCodePoint(c);
	                        c = snext();
	                } while (!isEndOfLine(c));
	                return res.toString();
	        }

	        public boolean isSpaceChar(int c)
	        {
	                if (filter != null)
	                        return filter.isSpaceChar(c);
	                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	        }

	        private boolean isEndOfLine(int c)
	        {
	                return c == '\n' || c == '\r' || c == -1;
	        }

	        public interface SpaceCharFilter
	        {
	                public boolean isSpaceChar(int ch);
	        }

	    }
		
		static class Debugger{
			public void n(int x) {
				out.println(x);
			}
			
			public void a(int[] a) {
		        StringBuilder sb = new StringBuilder();
		        for(int i=0;i<a.length;i++) {
		        		sb.append(a[i]+" ");
		        }
		        out.println(sb.toString());
			}
		}
	
		
}


class Pair { 
   int x; 
   int y; 
   // Constructor 
   public Pair(int x, int y) 
   { 
       this.x = x; 
       this.y = y; 
   } 
	@Override
	public boolean equals(Object o) {
	    if (this == o) return true;
	    if (!(o instanceof Pair)) return false;
	    Pair p = (Pair) o;
	    return x == p.x && y == p.y;
	}	
	@Override
	public int hashCode() {
		return (""+x+"-"+y).hashCode();
	}	
} 
