def findMinAndMax(L):
    if L==[]:
        return(None,None)
    min=float('inf')
    max=float('-inf')
    for i in L:
        if i<min:
            min=i
        if i>max:
            max=i
    return(min,max)

if findMinAndMax([]) != (None, None):
    print('测试失败1!')
elif findMinAndMax([7]) != (7, 7):
    print('测试失败2!')
elif findMinAndMax([7, 1]) != (1, 7):
    print('测试失败3!')
elif findMinAndMax([7, 1, 3, 9, 5]) != (1, 9):
    print('测试失败4!')
else:
    print('测试成功!')