# Enter your code here. Read input from STDIN. Print output to STDOUT
def check(np,t):
    l00=(-1,-1)
    l01=(-1,-1)
    l11=(-1,-1)
    l10=(-1,-1)
    
    maxl=-1
    maxr=-1
    
    for i in sorted(t):
        if maxl==-1 and maxr==-1:
            maxl=i[0]
            maxr=i[1]
            continue
        if i[0]!=maxl and i[0]!=maxr and i[1]!=maxl and i[1]!=maxr:
            #print (maxl,maxr)
            #print (i[0],i[1])
            return "NO"
        
        if i[0]==maxl or i[1]==maxr:
            maxl=max(maxl,i[0])
            maxr=max(maxr,i[1])
            
        
        
    return "YES"
        
    


T=input()
for i in range(T):
    np=input()
    t=[]
    for j in range(np):
        t.append(map(int,raw_input().strip().split()))
    print check(np,t)