Programming

Last time, we moved the tests for our test-driven factorial function from basic assert statements to being run by Python’s unittest module:

import unittest
from factorial import factorial

class TestFactorial(unittest.TestCase):

Last time, we built a factorial function in a test-driven style using Python’s assert statement:

def factorial(n):
    if n < 0:
        raise ValueError('Factorial of negative is undefined')
    return n * factorial(n-1) if n else 1

In part one, we started writing a factorial function in the test-driven style. We depend on the humble “assert” statement to run our tests and we ended with this:

def factorial(n):
    return n * factorial(n-1) if n else 1