t=int(input())
for _ in range(t):
  n=int(input())
  xy=[input().split()for _ in range(n)]
  ok=0
  bmin=1<<60
  bmax=0
  bnxt=1<<60
  for x,y in xy:
    if'a'==x:
      if'a'in y:
        ok=1
        break
      bmax=max(bmax,len(y))
      continue
    if'a'in y and'a'not in x:
      bmin=min(bmin,len(x))
    elif'a'not in x+y:
      bnxt=min(bnxt,len(x))
  if bnxt<=bmin:
    bmax=1<<60
  if ok or bmin<=bmax:
    print('Yes')
  else:
    print('No')