import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.PriorityQueue;



import java.util.*;

public class snippet {
	public static class pair implements Comparable<pair> {
		int a;
		int b;
		int id;

		pair(int x, int y,int id) {

			a = x;
			b = y;
			this.id=id;

		}

		public pair() {

		}

		public int compareTo(pair o) {
			// TODO Auto-generated method stub

			if (this.a / block == o.a / block)
				return ((this.a/block)%2!=0)?(this.b-o.b):(o.b-this.b);
			return this.a - o.a;
		}
	}
	static int mod = (int) 1e9 + 7;
	static ArrayList<Integer> gr[];
	static int ar[];
	static Scanner sc = new Scanner(System.in);
	static StringBuilder out = new StringBuilder();

	static int[] ti=new int[1000000];
	static int time=0;
	static int block=250;
	static int []dp;
	
	static int []dx= {1,-1,0,0};
	static int []dy= {0,0,1,-1};
			
			
	static char ch[][];
	public static void main(String[] args) throws IOException {
		int t=sc.nextInt();
		while (t-- > 0) {
			
			
			int n=sc.nextInt();
			int m=sc.nextInt();
			ch=new char[n][m];
		
			for(int i=0;i<n;i++) {
				
					String s=sc.next();
					for(int j=0;j<m;j++) {
						ch[i][j]=s.charAt(j);
					} 
				
			}
			boolean ok=true;
			for(int i=0;i<n;i++) {
				for(int j=0;j<m;j++) {
					if(ch[i][j]=='B') {
						for(int dir=0;dir<4;dir++) {
							int r=i+dx[dir];
							int c=j+dy[dir];
							if(r>=0 && c>=0 && r<n && c<m) {
								if(ch[r][c]=='.') {
									ch[r][c]='#';
								}
								if(ch[r][c]=='G')ok=false;
							}
					}
				}
					if(!ok)break;
			}
				if(!ok)break;
		}
				
				if(!ok) {
				out.append("No\n");
					continue;
				}
				
		trac=new int [52][52];
		for(int [] a:trac)Arrays.fill(a, -1);
		ok=true;
		for(int i=0;i<n;i++) {
			for(int j=0;j<m;j++) {
				if(trac[i][j]!=-1)continue;
				if(ch[i][j]=='G') {
					
					visited[i][j]=true;
					ok=solve(i,j,n,m);
					visited[i][j]=false;
				}
				if(!ok)break;
			}
			if(!ok)break;
		}
		
		if(ok)out.append("Yes\n");
		else out.append("No\n");
			 
			
	}
		System.out.println(out);
}
	
	static  boolean  visited [][]=new boolean[51][51];
	
	static int trac[][];
		static boolean solve(int i,int j, int n,int m) {
			if(i==n-1 && j==m-1)return true;
			
			
			if(trac[i][j]!=-1)return trac[i][j]==1?true:false;
			boolean ans=false;
			for(int dir=0;dir<4;dir++) {
				int r=i+dx[dir];
				int c=j+dy[dir];
				if(r>=0 && c>=0 && r<n && c<m &&!visited[r][c]) {
					visited[r][c]=true;
					if(ch[r][c]=='.' || ch[r][c]=='G')
					ans=solve(r,c,n,m);
					visited[r][c]=false;
				}
				
				if(ans==true)break;
			}
			
		trac[i][j]=ans==true?1:0;
		return ans;
			
		}
	
	
//	static Reader sc=new Reader();
	static class Reader {
		final private int BUFFER_SIZE = 1 << 16;
		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer, bytesRead;

		public Reader() {
			din = new DataInputStream(System.in);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public Reader(String file_name) throws IOException {
			din = new DataInputStream(new FileInputStream(file_name));
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public String readLine() throws IOException {
			byte[] buf = new byte[64]; // line length
			int cnt = 0, c;
			while ((c = read()) != -1) {
				if (c == '\n')
					break;
				buf[cnt++] = (byte) c;
			}
			return new String(buf, 0, cnt);
		}

		public int nextInt() throws IOException {
			int ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');

			if (neg)
				return -ret;
			return ret;
		}

		public long nextLong() throws IOException {
			long ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');
			if (neg)
				return -ret;
			return ret;
		}

		public double nextDouble() throws IOException {
			double ret = 0, div = 1;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();

			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');

			if (c == '.') {
				while ((c = read()) >= '0' && c <= '9') {
					ret += (c - '0') / (div *= 10);
				}
			}

			if (neg)
				return -ret;
			return ret;
		}

		private void fillBuffer() throws IOException {
			bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
			if (bytesRead == -1)
				buffer[0] = -1;
		}

		private byte read() throws IOException {
			if (bufferPointer == bytesRead)
				fillBuffer();
			return buffer[bufferPointer++];
		}

		public void close() throws IOException {
			if (din == null)
				return;
			din.close();
		}
	}


}