python/exercises/practice/collatz-conjecture/collatz_conjecture_test.py

import unittest

from collatz_conjecture import (
    steps,
)

# Tests adapted from `problem-specifications//canonical-data.json`


class CollatzConjectureTest(unittest.TestCase):
    def test_zero_steps_for_one(self):

        self.assertEqual(steps(1), 0)

    def test_divide_if_even(self):

        self.assertEqual(steps(16), 4)

    def test_even_and_odd_steps(self):

        self.assertEqual(steps(12), 9)

    def test_large_number_of_even_and_odd_steps(self):

        self.assertEqual(steps(1000000), 152)

    def test_zero_is_an_error(self):

        with self.assertRaises(ValueError) as err:
            steps(0)
        self.assertEqual(type(err.exception), ValueError)
        self.assertEqual(err.exception.args[0], "Only positive numbers are allowed")

    def test_negative_value_is_an_error(self):

        with self.assertRaises(ValueError) as err:
            steps(-15)
        self.assertEqual(type(err.exception), ValueError)
        self.assertEqual(err.exception.args[0], "Only positive numbers are allowed")