# Enter your code here. Read input from STDIN. Print output to STDOUT
cases=int(input())
for case in range(cases):
    n=int(input())
    mi_x=100000
    mi_y=100000
    ma_x=-100000
    ma_y=-100000
    lines=[]
    for l in range(n):
        line=map(int,raw_input().strip().split())
        lines.append(line)
        if mi_x>line[0]:
            mi_x=line[0]
            pass
        if ma_x<line[0]:
            ma_x=line[0]
            pass
        if mi_y>line[1]:
            mi_y=line[1]
            pass
        if ma_y<line[1]:
            ma_y=line[1]
            pass
        pass
    flag=0
    for line in lines:
        if (line[0]==ma_x or line[0]==mi_x) and (ma_y==line[1] or mi_y==line[1]):
            continue
            pass
        elif (line[0]==ma_x or line[0]==mi_x):
            if (line[1]<=ma_y and line[1]>=mi_y):
                continue
                pass
            else:
                flag=1
                print 'NO'
                break
                pass
            pass
        elif (line[1]==ma_y or line[1]==mi_y):
            if (line[0]<=ma_x and line[0]>=mi_x):
                continue
                pass
            else:
                flag=1
                print 'NO'
                break
                pass
            pass
        else:
            print 'NO'
            flag=1
            break
            pass
        pass
    if flag==1:
        pass
    else:
        print 'YES'
        pass
    pass
pass