Hi there!
While receiving mentoring to improve my code in Perfect Numbers, I noticed that exercism will allow code that covers all unit tests, but actually incorrectly computes some aliquot sums.
Consider this function computing the aliquot sum:
def compute_aliquot_sum(number):
if number == 1:
return 0
aliquot_sum = 1
i = 2
while i * i < number:
if number % i == 0:
aliquot_sum += i + number // i
i += 1
#if i * i == number:
#aliquot_sum += i
return aliquot_sum
This code (with another function for classification) will pass all unit tests, but only uncommenting those two lines will compute all of the correct aliquot sums (as far as I know). Luckily, in the range from 1 to 10,000,000 I found exactly four edge cases where the classification will be incorrect:
196, correct: abundant, aliquot sum: 203, incorrect: deficient, incorrect aliquot sum: 189
13456, correct: abundant, aliquot sum: 13545, incorrect: deficient, incorrect aliquot sum: 13429
15376, correct: abundant, aliquot sum: 15407, incorrect: deficient, incorrect aliquot sum: 15283
1032256, correct: abundant, aliquot sum: 1032383, incorrect: deficient, incorrect aliquot sum: 1031367
I propose adding at least one of those four numbers to the unit tests to root out incorrect solutions.
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