INF = 1<<60

for _ in range(int(input())):
    N = int(input())
    X, Y = map(list, zip(*[list(input().split()) for _ in range(N)]))

    flag = False
    MAX = 0
    for i in range(N):
        if X[i] != "a":
            continue
        if "a" in Y[i]:
            print("Yes")
            flag = True
            break
        MAX = max(MAX, len(Y[i]))
    if flag:
        continue
    if MAX == 0:
        print("No")
        continue
    for i in range(N):
        if len(X[i]) <= MAX and "a" not in X[i] and "a" not in Y[i]:
            flag = True
            print("Yes")
            break
    if flag:
        continue
    for i in range(N):
        if len(X[i]) <= MAX and "a" not in X[i] and "a" in Y[i]:
            print("Yes")
            break
    else:
        print("No")