from collections import defaultdict
T = int(input())
for _ in range(T):
    N = int(input())

    d = defaultdict(list)
    only_b = 10**18
    for _ in range(N):
        x,y = input().split()
        d[x].append(y)
        if(len(set(x)) == 1 and x[0] == "b"):
            only_b = min(only_b,len(x))

    if("a" not in d):
        print("No")
        continue
    
    flag = False
    B_MAX_LEN = -1
    for i in d["a"]:
        if("a" in i):flag = True
        B_MAX_LEN = max(B_MAX_LEN,len(i))
    
    if(flag):
        print("Yes")
        continue
    
    if(only_b <= B_MAX_LEN):
        print("Yes")
    else:
        print("No")