use proconio::input;
use std::io::Write;

fn main() {
    let mut writer = std::io::BufWriter::new(std::io::stdout().lock());

    input! { t: usize }

    for _ in 0..t {
        let ans = if solve() { "Yes" } else { "No" };
        writeln!(writer, "{ans}").unwrap();
    }
}

fn solve() -> bool {
    input! {
        n: usize,
        pairs: [(String, String); n]
    }

    let mut x_b_min_len = usize::MAX;
    let mut y_b_max_len = 0;
    for (x, y) in &pairs {
        if x == "a" {
            if y.contains("a") {
                return true;
            }
            y_b_max_len = y_b_max_len.max(y.len());
        }

        if !x.contains("a") {
            x_b_min_len = x_b_min_len.min(x.len());
        }
    }

    x_b_min_len <= y_b_max_len
}