T=int(input())
for _ in range(T):
  n=int(input())
  p=[]
  for i in range(n):
    x,y=input().split()
    p+=[(x,y)]
  if all(x!="a" for x,y in p):
    print("No")
    continue
  if any("a" in y for x,y in p if x=="a"):
    print("Yes")
    continue
  b=max([len(y) for x,y in p if x=="a"]+[0])
  if b>=min([len(x) for x,y in p if "a" not in x]+[10**10]):
    print("Yes")
    continue
  print("No")