t=int(input())
for _ in range(t):
    n=int(input())
    ok=False;
    x=[]
    y=[]
    for _ in range(n):
        xx,yy=input().split()
        x.append(xx)
        y.append(yy)
    ok2=False
    for i in range(n):
        if x[i]=='a':
            ok2=True
            if 'a' in y[i]:
                ok=True
    if ok:
        print("Yes")
        continue
    elif not ok2:
        print("No")
        continue
    mx=0
    mn=10**18
    for i in range(n):
        if x[i]=='a':
            mx=max(mx,len(y[i]))
        if 'a' not in x[i]:
            mn=min(mn,len(x[i]))
    if mx>=mn:
        print("Yes")
    else:
        print("No")