Katacode FizzBuzz with test

fizzbuzz.py

def fizzbuzz(number):
    value = str()
    if number % 3 == 0:
        value += 'fizz'
    if number % 5 == 0:
        value += 'buzz'
    return value or number

fizzbuzz_test.py

import unittest
from fizzbuzz import fizzbuzz

class TestFizzBuzz(unittest.TestCase):

    def test_simple_number(self):
        self.assertEqual(fizzbuzz(1), 1)
        self.assertEqual(fizzbuzz(2), 2)
        self.assertEqual(fizzbuzz(4), 4)

    def test_fizz(self):
        self.assertEqual(fizzbuzz(3), 'fizz')
        self.assertEqual(fizzbuzz(6), 'fizz')
        self.assertEqual(fizzbuzz(9), 'fizz')

    def test_buzz(self):
        self.assertEqual(fizzbuzz(5), 'buzz')
        self.assertEqual(fizzbuzz(10), 'buzz')
        self.assertEqual(fizzbuzz(20), 'buzz')

    def test_fizzbuzz(self):
        self.assertEqual(fizzbuzz(15), 'fizzbuzz')
        self.assertEqual(fizzbuzz(30), 'fizzbuzz')
        self.assertEqual(fizzbuzz(45), 'fizzbuzz')


if __name__ == '__main__':
    unittest.main()