def solve():
    N = int(input())
    X, Y = [None] * N, [None] * N

    for i in range(N):
        X[i], Y[i] = input().split()

    if "a" not in X:
        print("No")
        return

    if any(x == "a" and "a" in y for x, y in zip(X, Y)):
        print("Yes")
        return

    max_yb = max(len(y) for x, y in zip(X, Y) if x == "a")
    min_xb = min(len(x) for x in X if all(_x == "b" for _x in x))

    if max_yb >= min_xb:
        print("Yes")
    else:
        print("No")


if __name__ == "__main__":
    T = int(input())
    for _ in range(T):
        solve()