#include<bits/stdc++.h>
using namespace std;
int main(){
	int t;
	cin>>t;
	while(t--){
		int n;
		cin>>n;
		bool a=0;
		bool has_a=0;
		int bbb=-1;
		int bb=1<<20;
		vector<string>x(n),y(n);
		for(int i=0;i<n;i++){
			cin>>x[i]>>y[i];
			if(x[i]=="a"){
				a=1;
				if(y[i].find('a')!=-1){
					has_a=1;
				}else{
					bbb=max(bbb,(int)y[i].size());
				}
			}
			if(x[i].find('a')==-1){
				bb=min(bb,(int)x[i].size());
			}
		}
		bool ok=a&&(has_a||bbb>=bb);
		cout<<(ok?"Yes":"No")<<'\n';
	}
}