TT = int(input())

for loop in range(TT):

    N = int(input())

    ans = False

    a2b = 0
    b2a = 0
    b2min = float("inf")

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

        if X == "a" and "a" in Y:
            ans = True

        elif X == "a":
            a2b = max(a2b, len(Y))

        elif "a" not in X:
            b2min = min(b2min,len(X))

    if a2b >= b2min:
        ans = "Yes"

    if ans:
        print ("Yes")
    else:
        print ("No")