def solve(turn):
    
    n = int(input())
    X,Y=[],[]
    found = True
    for _ in range(n):
        x,y=input().split()
        X.append(x)
        Y.append(y)
    xa = False # xにaがある
    from_a_maxlenbb = 0
    for i in range(n):
        if X[i]=="a":
            xa = True
            
            for c in Y[i]:
                if c == "a":
                    print(f"turn={turn+1},x[i]=a and a in y[i]")
                    print('Yes')
                    return 
                    
            else:
                # x[i]がaの時、y[i]=bbbbb...bbbb
                from_a_maxlenbb = max(from_a_maxlenbb, len(Y[i]))

                    
    
    if not xa:
        print('No') # x[i]=aがない
        return

    xbb_minlen = 10**10
    for i in range(n):
        # a->..a..はok
        # a->b..bを考える
        # x[i]=b..bの必要性がある
        # x[i]=b..bがa->b..bのb連続列の長さ以下である必要がある
        allb = True
        for c in X[i]:
            if X[i]=="a":
                break
            allb=False
        if allb:
            #全てb
            xbb_minlen=min(xbb_minlen,len(X[i]))
    # x[i]=aでY[i]=bb.bb >= x[i]==bb..bb 
    """debugprint"""
    # print(f"turn,a2bbMl,bbml={turn,from_a_maxlenbb,xbb_minlen}")

    if from_a_maxlenbb >= xbb_minlen:
        print('Yes')
    else:
        print('No')



    pass

t = int(input())
for i in range(t):
    solve(i)