INF = float("inf")


def solve():
    N = int(input())
    X, Y = [], []

    for _ in range(N):
        x, y = input().split()
        X.append(x)
        Y.append(y)

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

    min_bx_len = INF
    max_by_len = 0

    for i in range(N):
        if X[i] == "a":
            if "a" in Y[i]:
                print("Yes")
                return

            max_by_len = max(max_by_len, len(Y[i]))

        if all(c == "b" for c in X[i]):
            min_bx_len = min(min_bx_len, len(X[i]))

    if min_bx_len <= max_by_len:
        print("Yes")
    else:
        print("No")


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