from math import isqrt
Q=int(input())
for _ in range(Q):
  N=int(input())
  ans=False
  z=0
  result='No'
  K=10**10
  for i in range(N):
    S,T=input().split()
    if S=='a':
      ans=True
      for j in range(len(T)):
        if T[j]=='a':
          result='Yes'
          break
      z=max(z,len(T))
    if S=='b'*(len(S)):
      K=min(K,len(S))
  if z>=K:
    result='Yes'
  print(result)