#include<bits/stdc++.h>
using namespace std;
#define rep(i,x,y) for (int i=(x);i<=(y);++i)
#define per(i,x,y) for (int i=(x);i>=(y);--i)
typedef long long ll;
void solve() {
	int n, m;
	cin >> n >> m;
	bool ok = true;
	int dx[4] = {1, 0, -1, 0};
	int dy[4] = {0, 1, 0, -1};
	string s = "ULDR";
	vector<vector<char>> mp(n + 1, vector<char>(m + 1));
	rep(i, 1, n) rep(j, 1, m) {
		cin >> mp[i][j];
		if (mp[i][j] == '.') {
			if (i != 1 || j != m) {
				ok = false;
			}
		}
	}
	if (!ok) {
		cout << "No\n";
		return;
	}
	if (mp[1][m] != '.') {
		cout << "No\n";
		return;
	}
	function<bool(int, int)> check = [&](int i, int j) {
		char c = mp[i][j];
		int x = i, y = j;
		if (c == 'C' || c == '.') return false;
		if (c == 'L' ) y--;
		else if (c == 'R') y++;
		else if (c == 'U') x--;
		else if (c == 'D') x++;
		if (x >= 1 && x <= n && y >= 1 && y <= m) {
			if (mp[x][y] == 'C') return true;
			else return false;
		}
		return false;
	};
	rep(i, 1, n) {
		rep(j, 1, m) {
			char c = mp[i][j];
			if (c == 'C') {
				int cnt = 0;
				rep(k, 0, 3) {
					int x = i + dx[k];
					int y = j + dy[k];
					if (x >= 1 && x <= n && y >= 1 && y <= m && mp[x][y] == s[k]) cnt++;
				}
				if (cnt != 2) {
					cout << "No\n";
					return ;
				}
			} else if (c != '.') {
				if (!check(i, j)) {
					cout << "No\n";
					return;
				}
			}
		}
	}
	cout << "Yes\n";
	return;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t = 1;
	cin >> t;
	while (t--) solve();
	return 0;
}
/*
2
4 4
CLD.
UDCL
DCLD
CLRC
2 3
DRC
CLU
*/