#include<stdio.h>
#include<algorithm>
#include<vector>
#include<string>
constexpr int N{200};
char str[N+5];
int a[N+5][N+5];
int b[N+5][N+5];
void solve() {
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) {
        scanf("%s",str+1);
        for(int j=1;j<=m;j++) {
            a[i][j]=str[j]=='B';
        }
    }
    const auto flip([&]()->void {
        for(int i=1;i<=n;i++) {
            for(int j=1;j<=m;j++) {
                a[i][j]^=1;
            }
        }
    });
    const auto check([&]()->bool {
        std::vector<std::string> opt;
        const auto copy([&]()->void {
            for(int i=1;i<=n;i++) {
                std::copy(a[i]+1,a[i]+m+1,b[i]+1);
            }
        });
        const auto pred([&]()->bool {
            for(int i=1;i<=n;i++) {
                for(int j=1;j<=m;j++) {
                    if(b[i][j]==1) {
                        return false;
                    }
                }
            }
            return true;
        });
        const auto move([&]()->void {
            std::string s;
            int j{1};
            for(int i=1;i<n;i++) {
                int k{m};
                while(k>=1&&b[i][k]==0) {
                    --k;
                }
                b[i][j]^=1;
                while(j<k) {
                    b[i][++j]^=1;
                    s.push_back('R');
                }
                s.push_back('D');
            }
            b[n][j]^=1;
            while(j<m) {
                b[n][++j]^=1;
                s.push_back('R');
            }
            opt.emplace_back(s);
        });
        copy();
        while(opt.size()!=4&&!pred()) {
            move();
        }
        if(pred()) {
            puts("YES");
            printf("%d\n",int(opt.size()));
            for(auto &s:opt) {
                printf("%s\n",s.c_str());
            }
            return true;
        }
        return false;
    });
    if(!check()&&(flip(),!check())) {
        puts("NO");
    }
}
int main() {
    int t;
    scanf("%d",&t);
    while(t--) {
        solve();
    }
    return 0;
}