lotto.py

import unittest

def bn(draws=None, balls=None):
	#error message for missing input
	if draws == None or balls == None: return "Missing Input" 
	#error message for negative input
	if draws < 0 or balls < 0: return "Input has to be a number >= 0" 
	#error message if draws > balls
	if balls<draws: return "Input number for draws has to be <= input number for balls" 
	#defining the factorial function
	def fact(num):
		return 1 if num == 0 else num*fact(num-1)
	#calculating the bn with fact
	return fact(balls) / (fact(draws)*fact(balls-draws))

#unittests
class TestingFunctionBio(unittest.TestCase):

	def test_negativity(self):
		self.assertEqual(bn(-1,0), 'Input has to be a number >= 0')
		self.assertEqual(bn(12,-1), 'Input has to be a number >= 0')

	def test_drawsSmallerThanBalls(self):
		self.assertEqual(bn(4,1), 'Input number for draws has to be <= input number for balls')

	def test_missingInput(self):
		self.assertEqual(bn(), 'Missing Input')
		self.assertEqual(bn(12), 'Missing Input')

	def test_lotto(self):
		self.assertEqual(bn(6,49), 13983816)

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