T=int(input())
for _ in range(T):
  N=int(input())
  ans='No'
  c=0;A=[10**20];f=0;d=10**20
  for i in range(N):
    a,b=input().split()
    if ans=='No':
      if 'a' not in a and 'a' not in b:
        f=1
        d=min(d,len(a))
      if a=='a':
        if 'a' in b:
          ans='Yes'
        else:
          c=max(c,len(b))
      if a==len(a)*'b' and 'a' in b:
        A.append(len(a)) 
  if f==1 and d<=c:
    c=10**19
    
  if min(A)<=c:
    ans='Yes'
  
    
  print(ans)