// -*- coding:utf-8-unix -*-
// #![feature(map_first_last)]
#![allow(dead_code)]
#![allow(unused_imports)]
#![allow(unused_macros)]
// use core::num;
use std::cmp::*;
use std::fmt::*;
use std::hash::*;
use std::io::BufRead;
use std::iter::FromIterator;
use std::*;
use std::{cmp, collections, fmt, io, iter, ops, str};
const INF: i64 = 1223372036854775807;
const UINF: usize = INF as usize;
const LINF: i64 = 2147483647;
const INF128: i128 = 1223372036854775807000000000000;
const MOD1: i64 = 1000000007;
const MOD9: i64 = 998244353;
const MOD: i64 = MOD9;
// const MOD: i64 = MOD2;
const UMOD: usize = MOD as usize;
const M_PI: f64 = 3.14159265358979323846;
const NINF: i64 = -(1i64 << 60);

// use proconio::input;
// const MOD: i64 = INF;

use cmp::Ordering::*;
use std::collections::*;

use std::io::stdin;
use std::io::stdout;
use std::io::Write;

macro_rules! p {
    ($x:expr) => {
        //if expr
        println!("{}", $x);
    };
}

macro_rules! vp {
    // vector print separate with space
    ($x:expr) => {
        println!(
            "{}",
            $x.iter()
                .map(|x| x.to_string())
                .collect::<Vec<_>>()
                .join(" ")
        );
    };
}

macro_rules! d {
    ($x:expr) => {
        eprintln!("{:?}", $x);
    };
}
macro_rules! yn {
    ($val:expr) => {
        if $val {
            println!("Yes");
        } else {
            println!("No");
        }
    };
}

macro_rules! map{
    // declear btreemap
    ($($key:expr => $val:expr),*) => {
        {
            let mut map = ::std::collections::BTreeMap::new();
            $(
                map.insert($key, $val);
            )*
            map
        }
    };
}

macro_rules! set{
    // declear btreemap
    ($($key:expr),*) => {
        {
            let mut set = ::std::collections::BTreeSet::new();
            $(
                set.insert($key);
            )*
            set
        }
    };
}

//input output
#[allow(dead_code)]
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

#[allow(dead_code)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

#[allow(dead_code)]
fn read_mat<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

#[allow(dead_code)]
fn readii() -> (i64, i64) {
    let mut vec: Vec<i64> = read_vec();
    (vec[0], vec[1])
}

#[allow(dead_code)]
fn readiii() -> (i64, i64, i64) {
    let mut vec: Vec<i64> = read_vec();
    (vec[0], vec[1], vec[2])
}
#[allow(dead_code)]
fn readuu() -> (usize, usize) {
    let mut vec: Vec<usize> = read_vec();
    (vec[0], vec[1])
}

#[allow(dead_code)]
fn readff() -> (f64, f64) {
    let mut vec: Vec<f64> = read_vec();
    (vec[0], vec[1])
}

fn readcc() -> (char, char) {
    let mut vec: Vec<char> = read_vec();
    (vec[0], vec[1])
}

fn readuuu() -> (usize, usize, usize) {
    let mut vec: Vec<usize> = read_vec();
    (vec[0], vec[1], vec[2])
}

#[allow(dead_code)]
fn readiiii() -> (i64, i64, i64, i64) {
    let mut vec: Vec<i64> = read_vec();
    (vec[0], vec[1], vec[2], vec[3])
}

fn main() {
    let t: usize = read();
    for _ in 0..t {
        let n: usize = read();
        let mut x = Vec::new();
        let mut y = Vec::new();
        for _ in 0..n {
            let v = read_vec::<String>();
            x.push(v[0].clone());
            y.push(v[1].clone());
        }
        let mut has_a = false;
        let mut case2 = false;
        let mut max_blen = 0;
        let mut xset = HashSet::new();
        for i in 0..n {
            xset.insert(x[i].clone());
        }
        let mut all_b = HashSet::new();
        for i in 0..n {
            if x[i] == "a" {
                has_a = true;
                if y[i].contains('a') {
                    case2 = true;
                } else {
                    let mut allb = true;
                    for c in y[i].chars() {
                        if c != 'b' {
                            allb = false;
                        }
                    }
                    if allb {
                        max_blen = max(max_blen, y[i].len());
                    }
                }
            }
        }
        if max_blen != 0 {
            for i in 0..n {
                let mut all_b_x = true;
                for c in x[i].chars() {
                    if c != 'b' {
                        all_b_x = false;
                    }
                }
                if all_b_x && max_blen >= x[i].len() {
                    all_b.insert(x[i].clone());
                }
            }
        }
        if !has_a {
            p!("No");
            continue;
        }
        if case2 {
            p!("Yes");
            continue;
        }
        if max_blen != 0 {
            if all_b.len() > 0 {
                p!("Yes");
                continue;
            }
        }
        p!("No");
    }
}