#include<bits/stdc++.h>
#include<bits/extc++.h>
#define int long long
#define inf 0x3f3f3f3f3f3f3f3f
#define maxn 223
#define eps 1e-7
#define mod 1000000007
#define Mod 998244353
#define f(i,a,b) for(int i=a;i<=b;i++)
#define r(i,a,b) for(int i=a;i>=b;i--) 
#define fx(i,a,b,x) for(int i=a;i<=b;i+=x)
#define rx(i,a,b,x) for(int i=a;i>=b;i-=x) 
using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;
int T;
int n,m,res;
char G[maxn][maxn];
void solve(){
	scanf("%lld%lld",&n,&m);
	f(i,1,n){
		f(j,1,m){
			cin>>G[i][j];
			if(G[i][j]=='o')res+=(n+j-i-1)%2+1;
		}
	}
	printf("%s\n",res%3==0?"YES":"NO");
}
signed main(){
//	T=1;
	scanf("%lld",&T);
	while(T--)solve();
	return 0;
}