// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2")
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
//#define ull unsigned long long
//#define int long long
#define SZ(x) ((int)((x).size()))
#define ALL(x) (x).begin(),(x).end()
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 2000005
#define inf 0x3f3f3f3f

int n,m;
string s[maxn];
int a[205][205];

vector<string>res;
void op(int x,int y){
	string now;
	a[1][1]^=1;
	For(i,2,y) now+='R',a[1][i]^=1;
	For(i,2,x) now+='D',a[i][y]^=1;
	For(i,y+1,m) now+='R',a[x][i]^=1;
	For(i,x+1,n) now+='D',a[i][m]^=1;
	res.pb(now);
}

bool tmp[maxn];
bool chk(){
	For(i,2,n+m)tmp[i]=0;
	For(i,1,n)For(j,1,m)tmp[i+j]^=a[i][j];
	For(i,2,n+m)if(tmp[i]!=tmp[2])return 0;
	return 1;
}

void work()
{
	n=read(),m=read(); res.clear();
	For(i,0,n-1)cin>>s[i];
	For(i,1,n)For(j,1,m)a[i][j]=(s[i-1][j-1]=='B');
	if(!chk()){
		For(i,1,n)For(j,1,m)a[i][j]^=1;
		if(!chk()){
			puts("NO");
			return;
		}
	}
	
	For(j,1,m-1){
		Rep(i,n,2){
			if(a[i][j]){
				op(i,j);
			}
		}
	}
	if(a[n][m]) op(n,m);
	For(i,1,n)For(j,1,m)if(a[i][j]){
		puts("NO");
		return;
	}
	puts("YES");
	cout<<res.size()<<"\n";
	for(auto it:res) cout<<it<<"\n";
}

signed main()
{
	int T=read();
	while(T--)work();
	return 0;
}
/*

*/