尽管满足要求，Python单元测试仍失败

Question

I am doing an online python course that requires I complete some exercise to progress. The orginisers of this course says they have visible and hidden requirements a user must meet pass each test. In this case, the probelem statement is as follows:

Write a function called manipulate_data which will act as follows: When given a list of integers, return a list, where the first element is the count of positives numbers and the second element is the sum of negative numbers. NB: Treat 0 as positive.

I came up with this, which I believe passes the visible requirement except maybe line 6 of the unit test case

def manipulate_data(listinput):
    report = [0,0]
    if type(listinput) != list:
    #I may need some work here.. see unit test line 6
        assert "invalid argument" 
    for digit in listinput:
    #is an even number so we increment it by 1
        if digit >= 0 and type(digit) == int: 
            report[0] += 1
    #number is less than zero, adds it sum
        elif digit < 0 and type(digit) == int:
            report[1] += digit
    return report

EveryTime I run the code, I always get this Error message Indicating that my code passes 2 test out of three, which I assume is test_only_list_allowed(self) I am not really experienced with this kind of things and I need help.

Answer 1

The test shows that the code expected a string to be returned . assert raises an AssertionError exception instead. You want to return the same string as the assertEquals() test is looking for, so 'Only lists allowed' , not the msg argument (which is shown when the test fails ).

Instead of using assert use return , and return the expected string:

if type(listinput) != list:
    return "Only lists allowed" 

Note that normally you'd use isinstance() to test for types:

if not isinstance(listinput, list):
    return "Only lists allowed" 
for digit in listinput:
    if not isinstance(digit, int):
        continue
    if digit >= 0: 
        report[0] += 1
    elif digit < 0:
        report[1] += digit

I used a single test for integers instead of testing in each branch. You could even have a type that doesn't support comparison with 0 so you want to get that test out of the way first.