#include<bits/stdc++.h>
using namespace std;
#define int long long
typedef long long ll;


#pragma GCC optimize(2)
#define debug(a) cout<<#a<<'='<<a<<endl
#define rep(i,a,b) for(int i=a;i<b;i++)
#define repp(i,a,b) for(int i=a ;i<=b;i++)
#define per(i,b,a) for(int i=b;i>a;i--)
#define perr(i,b,a) for(int i=b;i>=a;i--)
#define pii pair<int,int>
#define mm memset
#define endl '\n'
#define ff first
#define ss second
#define pb push_back
#define INF 0x7fffffffffffffff

const double eps =1e-8;
const int mod=1e9+7;
const int N=5e2+2;

int a[N][N];

void fun(){
    int n,m;
    cin>>n>>m;
    int cnt=0;
    repp(i,1,n)
    {
    	repp(j,1,m)
    	{
    		char c;
    		cin>>c;
    		if(c=='.')a[i][j]=-1,cnt++;
    		else if(c=='C')a[i][j]=0;
    		else if(c=='L')a[i][j]=1;
    		else if(c=='R')a[i][j]=2;
    		else if(c=='U')a[i][j]=3;
    		else a[i][j]=4;
    	//	cout<<c<<' ';
		}//cout<<endl;
	}
	int yu=n*m%3;
	if(yu!=1 || a[1][m]!=-1||cnt!=1)
	{
		cout<<"No"<<endl;
		return ;
	}
	
	repp(i,1,n)
	{
		repp(j,1,m)
		{
			if(a[i][j]==0)
			{
				if(j+1<=m&&a[i][j+1]==1&&i+1<=n&&a[i+1][j]==3)
				{
					a[i][j]=a[i][j+1]=a[i+1][j]=-1;
				}
				else if(j+1<=m&&a[i][j+1]==1&&i-1>=1&&a[i-1][j]==4)
				{
					a[i][j]=a[i][j+1]=a[i-1][j]=-1;
				}
				else if(j-1>=1&&a[i][j-1]==2&&i-1>=1&&a[i-1][j]==4)
				{
					a[i][j]=a[i][j-1]=a[i-1][j]=-1;
				}
				else if(j-1>=1&&a[i][j-1]==2&&i+1<=n&&a[i+1][j]==3)
				{
					a[i][j]=a[i][j-1]=a[i+1][j]=-1;
				}
			}
		}
	}
	repp(i,1,n)
	{
		repp(j,1,m)
		{
			if(a[i][j]!=-1)
			{
				cout<<"No"<<endl;
				return ;
			}
		}
	}
	cout<<"Yes"<<endl;
	return ;
	
	
	
}

signed main(){

    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

	int t=1 ;
	cin>>t;

	while(t--){
		fun();
	}



}