OK, maybe crazy overkill and a little silly, but why not? Here's a Python FizzBuzz Acceptance Test:

import unittest
from fizzbuzzmodule import fizzbuzz 

class FizzBuzzAcceptanceTestCase(unittest.TestCase):
    Test that fizzbuzz(int) returns int
    unless multiple of 3 (then returns 'fizz')
           multiple of 5 (then returns 'buzz')
           multiple of both (then returns 'fizzbuzz')
    def test_business_as_usual(self):
        test that an integer >= 0 not evenly divisible
        by three or five returns the same
        self.assertEqual(fizzbuzz(1), 1)
        self.assertEqual(fizzbuzz(2), 2)
        self.assertEqual(fizzbuzz(4), 4)
        self.assertEqual(fizzbuzz(7), 7)
        self.assertEqual(fizzbuzz(998), 998)
    def test_fizz(self):
        '''evenly divisible by 3 returns fizz'''
        self.assertEqual(fizzbuzz(3), 'fizz')
        self.assertEqual(fizzbuzz(6), 'fizz')
        self.assertEqual(fizzbuzz(111), 'fizz')
        self.assertEqual(fizzbuzz(999), 'fizz')
    def test_buzz(self):
        '''evenly divisible by 5 returns buzz'''
        self.assertEqual(fizzbuzz(5), 'buzz')
        self.assertEqual(fizzbuzz(10), 'buzz')
        self.assertEqual(fizzbuzz(20), 'buzz')
        self.assertEqual(fizzbuzz(500), 'buzz')
    def test_fizz_buzz(self):
        '''evenly divisible by 3 and 5 returns fizzbuzz'''
        self.assertEqual(fizzbuzz(15), 'fizzbuzz')
        self.assertEqual(fizzbuzz(30), 'fizzbuzz')
        self.assertEqual(fizzbuzz(45), 'fizzbuzz')
        self.assertEqual(fizzbuzz(600), 'fizzbuzz')

    # def test_zero(self):
        # self.assertEqual(fizzbuzz(0), 'fizzbuzz') #??????

def main():

if __name__ == '__main__':

Typed up a little implementation that passes these tests:

def fizzbuzz(number):
    if number divisible by 3 return 'fizz';
    5, 'buzz'; both, fizzbuzz
    else return number
    if not number % 3:
        if not number % 5:
            return 'fizzbuzz'
            return 'fizz'
    if not number % 5:
        return 'buzz'
    return number

def main():
    for i in range(1, 101):
        print fizzbuzz(i)

And when I run the tests:

>>> unittest.main()
Ran 4 tests in 0.002s


And my question is, how would you augment the above? Would you find it useful to run this test on someone's code? Does it clearly define a clean API? Would it be preferable to return a consistent type instead of strings or ints?

Should I have done this differently? Have I not considered any edge or corner cases?

  • \$\begingroup\$ you should remove the code golf part, or post it on the Code Golf Stack Site. \$\endgroup\$
    – Malachi
    Commented Jan 10, 2014 at 6:04
  • 1
    \$\begingroup\$ No code golf! :) \$\endgroup\$
    – Aaron Hall
    Commented Jan 10, 2014 at 6:06

1 Answer 1


For something so simple, it might be less overkill to use the doctest module. Write the expected calls and outputs in the docstring, then run python -m doctest -v fizzbuzzmodule.py. There's no need to write a separate class.

I've written one of the tests to ensure that the function also works when called with decreasing arguments.

As for the function itself, I believe that the code reads better if you write number % 3 == 0 instead of not number % 3. I would also use a conditional expression, but that's just a matter of personal preference.

def fizzbuzz(number):
    if number divisible by 3 return 'fizz';
    5, 'buzz'; both, fizzbuzz
    else return number

    >>> fizzbuzz(1)
    >>> fizzbuzz(2)
    >>> fizzbuzz(3)
    >>> fizzbuzz(4)
    >>> fizzbuzz(5)
    >>> fizzbuzz(15)
    >>> [fizzbuzz(i) for i in range(31, 20, -1)]
    [31, 'fizzbuzz', 29, 28, 'fizz', 26, 'buzz', 'fizz', 23, 22, 'fizz']
    if number % 3 == 0:
        return 'fizzbuzz' if (number % 5 == 0) else 'fizz'
    if number % 5 == 0:
        return 'buzz'
    return number

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