import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.ArrayDeque;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author unknown
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        DSolveTheMaze solver = new DSolveTheMaze();
        solver.solve(1, in, out);
        out.close();
    }

    static class DSolveTheMaze {
        int[] dx = {-1, 0, 1, 0};
        int[] dy = {0, 1, 0, -1};
        char[][] mat;
        int n;
        int m;
        boolean[][] vis;

        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int ntc = in.nextInt();
            while ((ntc--) > 0) {
                n = in.nextInt();
                m = in.nextInt();
                int gc = 0;
                int bc = 0;
                mat = new char[n][m];
                vis = new boolean[n][m];
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < m; j++) {
                        char ch = in.nextCharacter();
                        if (ch == 'G') {
                            gc++;
                        }
                        if (ch == 'B') {
                            bc++;
                        }
                        mat[i][j] = ch;
                    }
                }
                if (gc == 0) {
                    out.println("Yes");
                    continue;
                }
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < m; j++) {
                        if (mat[i][j] == 'B') {
                            for (int k = 0; k < 4; k++) {
                                int newx = dx[k] + i;
                                int newy = dy[k] + j;
                                if (isvalid(newx, newy) && mat[newx][newy] == '.') {
                                    mat[newx][newy] = '#';
                                }
                            }
                        }
                    }
                }
                if (mat[n - 1][m - 1] == '.') {
                    mat[n - 1][m - 1] = '#';
                }
                bfs(n - 1, m - 1);
                boolean ok = true;
//            vis = new boolean[n][m];
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < m; j++) {
                        if (mat[i][j] == 'G' && !vis[i][j]) {
                            ok = false;
                            break;
                        } else if (mat[i][j] == 'B' && vis[i][j]) {
                            ok = false;
                            break;
                        }
                    }
                }
                if (ok) {
                    out.println("Yes");
                } else {
                    out.println("No");
                }
//            for(int i = )
            }
        }

        void bfs(int x, int y) {
            ArrayDeque<Integer> queue = new ArrayDeque<>();
            queue.addLast(x);
            queue.addLast(y);
            vis[x][y] = true;
            while (!queue.isEmpty()) {
                int u = queue.removeFirst();
                int v = queue.removeFirst();
                for (int i = 0; i < 4; i++) {
                    int newx = u + dx[i];
                    int newy = v + dy[i];
                    if (isvalid(newx, newy) && mat[newx][newy] != '#' && !vis[newx][newy]) {
//                    if(newx == n-1 && newy == m-1){
//                        return true;
//                    }
                        vis[newx][newy] = true;
                        queue.addLast(newx);
                        queue.addLast(newy);
                    }
                }
            }
//        return false;
        }

        boolean isvalid(int x, int y) {
            if (x < 0 || x >= n) {
                return false;
            }
            if (y < 0 || y >= m) {
                return false;
            }
            return true;
        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; ++i) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void println(Object... objects) {
            print(objects);
            writer.println();
        }

        public void close() {
            writer.close();
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

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

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

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public char nextCharacter() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            return (char) c;
        }

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

        }

    }
}

