#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000005
#define Inf64 1000000000000000001LL
int len(string s){
	int res = 0;
	int cur = 0;
	rep(i,s.size()){
		if(s[i]=='a')cur = 0;
		else cur++;
		res = max(res,cur);
	}
	return res;
	
}

int main(){
	
	int _t;
	cin>>_t;
	rep(_,_t){
		int n;
		cin>>n;
		vector<string> x(n),y(n);
		rep(i,n)cin>>x[i]>>y[i];
		int ma = -1;
		rep(i,n){
			if(x[i]!="a")continue;
			if(y[i]==string(y[i].size(),'b'))ma = max(ma,(int)y[i].size());
			else ma = Inf32;
		}
		if(ma==Inf32){
			cout<<"Yes"<<endl;
			continue;
		}
		if(ma==-1){
			cout<<"No"<<endl;
			continue;
		}
		rep(i,n){
			if(x[i]==string(x[i].size(),'b')&&ma >= x[i].size()){
				ma = -1;
				break;
			}
		}
		if(ma==-1){
			cout<<"Yes"<<endl;
			continue;
		}
		else{
			cout<<"No"<<endl;
		}
	}
}